-The tz database attempts to record the history and predicted future of
-all computer-based clocks that track civil time. To represent this
-data, the world is partitioned into regions whose clocks all agree
-about timestamps that occur after the somewhat-arbitrary cutoff point
-of the POSIX Epoch (1970-01-01 00:00:00 UTC). For each such region,
-the database records all known clock transitions, and labels the region
-with a notable location. Although 1970 is a somewhat-arbitrary
-cutoff, there are significant challenges to moving the cutoff earlier
-even by a decade or two, due to the wide variety of local practices
-before computer timekeeping became prevalent.
+The tz
+database attempts to record the history and predicted future of
+all computer-based clocks that track civil time.
+It organizes time zone and daylight saving time
+data by partitioning the world into regions
+whose clocks all agree about timestamps that occur after the POSIX Epoch
+(1970-01-01 00:00:00 UTC).
+The database labels each such region with a notable location and
+records all known clock transitions for that location.
+Although 1970 is a somewhat-arbitrary cutoff, there are significant
+challenges to moving the cutoff earlier even by a decade or two, due
+to the wide variety of local practices before computer timekeeping
+became prevalent.
@@ -52,200 +53,236 @@ However, the database is not designed for and does not suffice for
applications requiring accurate handling of all past times everywhere,
as it would take far too much effort and guesswork to record all
details of pre-1970 civil timekeeping.
-Athough some information outside the scope of the database is
+Although some information outside the scope of the database is
collected in a file backzone that is distributed along
with the database proper, this file is less reliable and does not
necessarily follow database guidelines.
-As described below, reference source code for using the tz database is
-also available. The tz code is upwards compatible with POSIX, an
-international standard for UNIX-like systems. As of this writing, the
-current edition of POSIX is:
-
- The Open Group Base Specifications Issue 7,
- IEEE Std 1003.1-2008, 2016 Edition.
+As described below, reference source code for using the
+tz database is also available.
+The tz code is upwards compatible with POSIX, an international
+standard for UNIX-like systems.
+As of this writing, the current edition of POSIX is: The Open
+Group Base Specifications Issue 7, IEEE Std 1003.1-2017, 2018
+Edition.
+Because the database's scope encompasses real-world changes to civil
+timekeeping, its model for describing time is more complex than the
+standard and daylight saving times supported by POSIX.
+A tz region corresponds to a ruleset that can
+have more than two changes per year, these changes need not merely
+flip back and forth between two alternatives, and the rules themselves
+can change at times.
+Whether and when a tz region changes its
+clock, and even the region's notional base offset from UTC, are variable.
+It does not always make sense to talk about a region's
+"base offset", since it is not necessarily a single number.
-
+
-
-
-
Names of time zone rules
+
+
Names of time zone rulesets
-Each of the database's time zone rules has a unique name.
+Each tz region has a unique name that
+corresponds to a set of time zone rules.
Inexperienced users are not expected to select these names unaided.
Distributors should provide documentation and/or a simple selection
-interface that explains the names; for one example, see the 'tzselect'
-program in the tz code. The
-Unicode Common Locale Data
-Repository contains data that may be useful for other
-selection interfaces.
+interface that explains the names; for one example, see the
+tzselect program in the tz code.
+The Unicode Common Locale Data
+Repository contains data that may be useful for other selection
+interfaces.
-The time zone rule naming conventions attempt to strike a balance
+The naming conventions attempt to strike a balance
among the following goals:
+
- Uniquely identify every region where clocks have agreed since 1970.
- This is essential for the intended use: static clocks keeping local
- civil time.
+ Uniquely identify every region where clocks have agreed since 1970.
+ This is essential for the intended use: static clocks keeping local
+ civil time.
- Indicate to experts where that region is.
+ Indicate to experts where that region is.
- Be robust in the presence of political changes. For example, names
- of countries are ordinarily not used, to avoid incompatibilities
- when countries change their name (e.g. Zaire→Congo) or when
- locations change countries (e.g. Hong Kong from UK colony to
- China).
+ Be robust in the presence of political changes.
+ For example, names of countries are ordinarily not used, to avoid
+ incompatibilities when countries change their name (e.g.,
+ Zaire→Congo) or when locations change countries (e.g., Hong
+ Kong from UK colony to China).
- Be portable to a wide variety of implementations.
+ Be portable to a wide variety of implementations.
- Use a consistent naming conventions over the entire world.
+ Use a consistent naming conventions over the entire world.
+
-Names normally have the
-form AREA/LOCATION,
-where AREA is the name of a continent or ocean,
-and LOCATION is the name of a specific
-location within that region. North and South America share the same
-area, 'America'. Typical names are
-'Africa/Cairo', 'America/New_York', and
-'Pacific/Honolulu'.
+Names normally have the form
+AREA/LOCATION, where
+AREA is the name of a continent or ocean, and
+LOCATION is the name of a specific location within that
+region.
+North and South America share the same area, 'America'.
+Typical names are 'Africa/Cairo',
+'America/New_York', and 'Pacific/Honolulu'.
+Some names are further qualified to help avoid confusion; for example,
+'America/Indiana/Petersburg' distinguishes Petersburg,
+Indiana from other Petersburgs in America.
-Here are the general rules used for choosing location names,
+Here are the general guidelines used for
+choosing tz region names,
in decreasing order of importance:
+
- Use only valid POSIX file name components (i.e., the parts of
- names other than '/'). Do not use the file name
- components '.' and '..'.
- Within a file name component,
- use only ASCII letters, '.',
- '-' and '_'. Do not use
- digits, as that might create an ambiguity with POSIX
- TZ strings. A file name component must not exceed 14
- characters or start with '-'. E.g.,
- prefer 'Brunei' to
- 'Bandar_Seri_Begawan'. Exceptions: see
- the discussion
- of legacy names below.
+ Use only valid POSIX file name components (i.e., the parts of
+ names other than '/').
+ Do not use the file name components '.' and
+ '..'.
+ Within a file name component, use only ASCII letters,
+ '.', '-' and '_'.
+ Do not use digits, as that might create an ambiguity with POSIX
+ TZ strings.
+ A file name component must not exceed 14 characters or start with
+ '-'.
+ E.g., prefer Asia/Brunei to
+ Asia/Bandar_Seri_Begawan.
+ Exceptions: see the discussion of legacy names below.
- A name must not be empty, or contain '//', or
- start or end with '/'.
+ A name must not be empty, or contain '//', or
+ start or end with '/'.
- Do not use names that differ only in case. Although the reference
- implementation is case-sensitive, some other implementations
- are not, and they would mishandle names differing only in case.
+ Do not use names that differ only in case.
+ Although the reference implementation is case-sensitive, some
+ other implementations are not, and they would mishandle names
+ differing only in case.
- If one name A is an initial prefix of another
- name AB (ignoring case), then B
- must not start with '/', as a
- regular file cannot have
- the same name as a directory in POSIX. For example,
- 'America/New_York' precludes
- 'America/New_York/Bronx'.
+ If one name A is an initial prefix of another
+ name AB (ignoring case), then B must not
+ start with '/', as a regular file cannot have the
+ same name as a directory in POSIX.
+ For example, America/New_York precludes
+ America/New_York/Bronx.
- Uninhabited regions like the North Pole and Bouvet Island
- do not need locations, since local time is not defined there.
+ Uninhabited regions like the North Pole and Bouvet Island
+ do not need locations, since local time is not defined there.
- There should typically be at least one name for each ISO 3166-1
- officially assigned two-letter code for an inhabited country
- or territory.
+ There should typically be at least one name for each ISO
+ 3166-1 officially assigned two-letter code for an inhabited
+ country or territory.
- If all the clocks in a region have agreed since 1970,
- don't bother to include more than one location
- even if subregions' clocks disagreed before 1970.
- Otherwise these tables would become annoyingly large.
+ If all the clocks in a region have agreed since 1970,
+ do not bother to include more than one location
+ even if subregions' clocks disagreed before 1970.
+ Otherwise these tables would become annoyingly large.
- Keep locations compact. Use cities or small islands, not countries
- or regions, so that any future time zone changes do not split
- locations into different time zones. E.g. prefer
- 'Paris' to 'France', since
- France has had multiple time zones.
+ Keep locations compact.
+ Use cities or small islands, not countries or regions, so that any
+ future changes do not split individual locations into different
+ tz regions.
+ E.g., prefer Europe/Paris to Europe/France,
+ since
+ France
+ has had multiple time zones.
- Use mainstream English spelling, e.g. prefer
- 'Rome' to 'Roma', and prefer
- 'Athens' to the Greek
- 'Îθήνα' or the Romanized
- 'AthÃna'.
- The POSIX file name restrictions encourage this rule.
+ Use mainstream English spelling, e.g., prefer
+ Europe/Rome to Europe/Roma, and
+ prefer Europe/Athens to the Greek
+ Europe/Îθήνα or the Romanized
+ Europe/AthÃna.
+ The POSIX file name restrictions encourage this guideline.
- Use the most populous among locations in a zone,
- e.g. prefer 'Shanghai' to
- 'Beijing'. Among locations with
- similar populations, pick the best-known location,
- e.g. prefer 'Rome' to 'Milan'.
+ Use the most populous among locations in a region,
+ e.g., prefer Asia/Shanghai to
+ Asia/Beijing.
+ Among locations with similar populations, pick the best-known
+ location, e.g., prefer Europe/Rome to
+ Europe/Milan.
- Use the singular form, e.g. prefer 'Canary' to 'Canaries'.
+ Use the singular form, e.g., prefer Atlantic/Canary to
+ Atlantic/Canaries.
- Omit common suffixes like '_Islands' and
- '_City', unless that would lead to
- ambiguity. E.g. prefer 'Cayman' to
- 'Cayman_Islands' and
- 'Guatemala' to
- 'Guatemala_City', but prefer
- 'Mexico_City' to 'Mexico'
- because the country
- of Mexico has several time zones.
+ Omit common suffixes like '_Islands' and
+ '_City', unless that would lead to ambiguity.
+ E.g., prefer America/Cayman to
+ America/Cayman_Islands and
+ America/Guatemala to
+ America/Guatemala_City, but prefer
+ America/Mexico_City to
+ America/Mexico
+ because the
+ country of Mexico has several time zones.
- Use '_' to represent a space.
+ Use '_' to represent a space.
- Omit '.' from abbreviations in names, e.g. prefer
- 'St_Helena' to 'St._Helena'.
+ Omit '.' from abbreviations in names.
+ E.g., prefer Atlantic/St_Helena to
+ Atlantic/St._Helena.
- Do not change established names if they only marginally
- violate the above rules. For example, don't change
- the existing name 'Rome' to
- 'Milan' merely because
- Milan's population has grown to be somewhat greater
- than Rome's.
+ Do not change established names if they only marginally violate
+ the above guidelines.
+ For example, do not change the existing name Europe/Rome to
+ Europe/Milan merely because Milan's population has grown
+ to be somewhat greater than Rome's.
- If a name is changed, put its old spelling in the
- 'backward' file.
- This means old spellings will continue to work.
+ If a name is changed, put its old spelling in the
+ 'backward' file.
+ This means old spellings will continue to work.
The file 'zone1970.tab' lists geographical locations used
-to name time
-zone rules. It is intended to be an exhaustive list of names for
-geographic regions as described above; this is a subset of the names
-in the data. Although a 'zone1970.tab' location's longitude
-corresponds to its LMT offset with one hour for every 15° east
-longitude, this relationship is not exact.
+to name tz regions.
+It is intended to be an exhaustive list of names for geographic
+regions as described above; this is a subset of the names in the data.
+Although a 'zone1970.tab' location's
+longitude
+corresponds to
+its local mean
+time (LMT) offset with one hour for every 15°
+east longitude, this relationship is not exact.
@@ -254,843 +291,1014 @@ and these older names are still supported.
See the file 'backward' for most of these older names
(e.g., 'US/Eastern' instead of 'America/New_York').
The other old-fashioned names still supported are
-'WET', 'CET', 'MET', and 'EET' (see the file 'europe').
+'WET', 'CET', 'MET', and
+'EET' (see the file 'europe').
Older versions of this package defined legacy names that are
-incompatible with the first rule of location names, but which are
-still supported. These legacy names are mostly defined in the file
-'etcetera'. Also, the file 'backward' defines the legacy names
-'GMT0', 'GMT-0' and 'GMT+0', and the file 'northamerica' defines the
-legacy names 'EST5EDT', 'CST6CDT', 'MST7MDT', and 'PST8PDT'.
+incompatible with the first guideline of location names, but which are
+still supported.
+These legacy names are mostly defined in the file
+'etcetera'.
+Also, the file 'backward' defines the legacy names
+'GMT0', 'GMT-0' and 'GMT+0',
+and the file 'northamerica' defines the legacy names
+'EST5EDT', 'CST6CDT',
+'MST7MDT', and 'PST8PDT'.
-Excluding 'backward' should not affect the other data. If
-'backward' is excluded, excluding 'etcetera' should not affect the
-remaining data.
+Excluding 'backward' should not affect the other data.
+If 'backward' is excluded, excluding
+'etcetera' should not affect the remaining data.
+
-
-
-
-
Time zone abbreviations
+
+
Time zone abbreviations
When this package is installed, it generates time zone abbreviations
like 'EST' to be compatible with human tradition and POSIX.
-Here are the general rules used for choosing time zone abbreviations,
+Here are the general guidelines used for choosing time zone abbreviations,
in decreasing order of importance:
+
+
- Use three to six characters that are ASCII alphanumerics or
- '+' or '-'.
- Previous editions of this database also used characters like
- '' and '?', but these
- characters have a special meaning to
- the shell and cause commands like
- 'set `date`'
- to have unexpected effects.
- Previous editions of this rule required upper-case letters,
- but the Congressman who introduced Chamorro Standard Time
- preferred "ChST", so lower-case letters are now allowed.
- Also, POSIX from 2001 on relaxed the rule to allow
- '-', '+',
- and alphanumeric characters from the portable character set
- in the current locale. In practice ASCII alphanumerics and
- '+' and '-' are safe in all locales.
-
- In other words, in the C locale the POSIX extended regular
- expression [-+[:alnum:]]{3,6} should match
- the abbreviation.
- This guarantees that all abbreviations could have been
- specified by a POSIX TZ string.
-
-
- Use abbreviations that are in common use among English-speakers,
- e.g. 'EST' for Eastern Standard Time in North America.
- We assume that applications translate them to other languages
- as part of the normal localization process; for example,
- a French application might translate 'EST' to 'HNE'.
+ Use three to six characters that are ASCII alphanumerics or
+ '+' or '-'.
+ Previous editions of this database also used characters like
+ space and '?', but these characters have a
+ special meaning to the
+ UNIX shell
+ and cause commands like
+ 'set
+ `date`'
+ to have unexpected effects.
+ Previous editions of this guideline required upper-case letters, but the
+ Congressman who introduced
+ Chamorro
+ Standard Time preferred "ChST", so lower-case letters are now
+ allowed.
+ Also, POSIX from 2001 on relaxed the rule to allow '-',
+ '+', and alphanumeric characters from the portable
+ character set in the current locale.
+ In practice ASCII alphanumerics and '+' and
+ '-' are safe in all locales.
-
These abbreviations (for standard/daylight/etc. time) are:
-ACST/ACDT Australian Central,
-AST/ADT/APT/AWT/ADDT Atlantic,
-AEST/AEDT Australian Eastern,
-AHST/AHDT Alaska-Hawaii,
-AKST/AKDT Alaska,
-AWST/AWDT Australian Western,
-BST/BDT Bering,
-CAT/CAST Central Africa,
-CET/CEST/CEMT Central European,
-ChST Chamorro,
-CST/CDT/CWT/CPT/CDDT Central [North America],
-CST/CDT China,
-GMT/BST/IST/BDST Greenwich,
-EAT East Africa,
-EST/EDT/EWT/EPT/EDDT Eastern [North America],
-EET/EEST Eastern European,
-GST Guam,
-HST/HDT Hawaii,
-HKT/HKST Hong Kong,
-IST India,
-IST/GMT Irish,
-IST/IDT/IDDT Israel,
-JST/JDT Japan,
-KST/KDT Korea,
-MET/MEST Middle European (a backward-compatibility alias for Central European),
-MSK/MSD Moscow,
-MST/MDT/MWT/MPT/MDDT Mountain,
-NST/NDT/NWT/NPT/NDDT Newfoundland,
-NST/NDT/NWT/NPT Nome,
-NZMT/NZST New Zealand through 1945,
-NZST/NZDT New Zealand 1946–present,
-PKT/PKST Pakistan,
-PST/PDT/PWT/PPT/PDDT Pacific,
-SAST South Africa,
-SST Samoa,
-WAT/WAST West Africa,
-WET/WEST/WEMT Western European,
-WIB Waktu Indonesia Barat,
-WIT Waktu Indonesia Timur,
-WITA Waktu Indonesia Tengah,
-YST/YDT/YWT/YPT/YDDT Yukon.
-
-
- For zones whose times are taken from a city's longitude, use the
-traditional xMT notation. The only abbreviation like this
-in current use is 'GMT'. The others are for timestamps before 1960,
-except that Monrovia Mean Time persisted until 1972. Typically,
-numeric abbreviations (e.g., '-004430' for MMT) would
-cause trouble here, as the numeric strings would exceed the POSIX length limit.
+
+ In other words, in the C locale the POSIX extended regular
+ expression [-+[:alnum:]]{3,6} should match the
+ abbreviation.
+ This guarantees that all abbreviations could have been specified by a
+ POSIX TZ string.
+
+
+
+ Use abbreviations that are in common use among English-speakers,
+ e.g., 'EST' for Eastern Standard Time in North America.
+ We assume that applications translate them to other languages
+ as part of the normal localization process; for example,
+ a French application might translate 'EST' to 'HNE'.
-
+ These abbreviations (for standard/daylight/etc. time) are:
+ ACST/ACDT Australian Central,
+ AST/ADT/APT/AWT/ADDT Atlantic,
+ AEST/AEDT Australian Eastern,
+ AHST/AHDT Alaska-Hawaii,
+ AKST/AKDT Alaska,
+ AWST/AWDT Australian Western,
+ BST/BDT Bering,
+ CAT/CAST Central Africa,
+ CET/CEST/CEMT Central European,
+ ChST Chamorro,
+ CST/CDT/CWT/CPT/CDDT Central [North America],
+ CST/CDT China,
+ GMT/BST/IST/BDST Greenwich,
+ EAT East Africa,
+ EST/EDT/EWT/EPT/EDDT Eastern [North America],
+ EET/EEST Eastern European,
+ GST Guam,
+ HST/HDT Hawaii,
+ HKT/HKST Hong Kong,
+ IST India,
+ IST/GMT Irish,
+ IST/IDT/IDDT Israel,
+ JST/JDT Japan,
+ KST/KDT Korea,
+ MET/MEST Middle European (a backward-compatibility alias for
+ Central European),
+ MSK/MSD Moscow,
+ MST/MDT/MWT/MPT/MDDT Mountain,
+ NST/NDT/NWT/NPT/NDDT Newfoundland,
+ NST/NDT/NWT/NPT Nome,
+ NZMT/NZST New Zealand through 1945,
+ NZST/NZDT New Zealand 1946–present,
+ PKT/PKST Pakistan,
+ PST/PDT/PWT/PPT/PDDT Pacific,
+ SAST South Africa,
+ SST Samoa,
+ WAT/WAST West Africa,
+ WET/WEST/WEMT Western European,
+ WIB Waktu Indonesia Barat,
+ WIT Waktu Indonesia Timur,
+ WITA Waktu Indonesia Tengah,
+ YST/YDT/YWT/YPT/YDDT Yukon.
+
+
+
+
+ For times taken from a city's longitude, use the
+ traditional xMT notation.
+ The only abbreviation like this in current use is 'GMT'.
+ The others are for timestamps before 1960,
+ except that Monrovia Mean Time persisted until 1972.
+ Typically, numeric abbreviations (e.g., '-004430' for
+ MMT) would cause trouble here, as the numeric strings would exceed
+ the POSIX length limit.
+
-
A few abbreviations also follow the pattern that
-GMT/BST established for time in the UK. They are:
+
-CMT/BST for Calamarca Mean Time and Bolivian Summer Time
-1890–1932, DMT/IST for Dublin/Dunsink Mean Time and Irish Summer Time
-1880–1916, MMT/MST/MDST for Moscow 1880–1919, and RMT/LST
-for Riga Mean Time and Latvian Summer time 1880–1926.
-An extra-special case is SET for Swedish Time (svensk
-normaltid) 1879–1899, 3° west of the Stockholm
-Observatory.
+
+ A few abbreviations also follow the pattern that
+ GMT/BST established for time in the UK.
+ They are:
+ CMT/BST for Calamarca Mean Time and Bolivian Summer Time
+ 1890–1932,
+ DMT/IST for Dublin/Dunsink Mean Time and Irish Summer Time
+ 1880–1916,
+ MMT/MST/MDST for Moscow 1880–1919, and
+ RMT/LST for Riga Mean Time and Latvian Summer time 1880–1926.
+ An extra-special case is SET for Swedish Time (svensk
+ normaltid) 1879–1899, 3° west of the Stockholm
+ Observatory.
+
- Use 'LMT' for local mean time of locations before the introduction
- of standard time; see "Scope of the
- tz database".
+ Use 'LMT' for local mean time of locations before the
+ introduction of standard time; see "Scope of the
+ tz database".
- If there is no common English abbreviation, use numeric offsets like
- -05 and +0830 that are
- generated by zic's %z notation.
+ If there is no common English abbreviation, use numeric offsets like
+ -05 and +0830 that are generated
+ by zic's %z notation.
- Use current abbreviations for older timestamps to avoid confusion.
- For example, in 1910 a common English abbreviation for UT +01
- in central Europe was 'MEZ' (short for both "Middle European
- Zone" and for "Mitteleuropäische Zeit" in German). Nowadays
- 'CET' ("Central European Time") is more common in English, and
- the database uses 'CET' even for circa-1910 timestamps as this
- is less confusing for modern users and avoids the need for
- determining when 'CET' supplanted 'MEZ' in common usage.
+ Use current abbreviations for older timestamps to avoid confusion.
+ For example, in 1910 a common English abbreviation for time
+ in central Europe was 'MEZ' (short for both "Middle European
+ Zone" and for "Mitteleuropäische Zeit" in German).
+ Nowadays 'CET' ("Central European Time") is more common in
+ English, and the database uses 'CET' even for circa-1910
+ timestamps as this is less confusing for modern users and avoids
+ the need for determining when 'CET' supplanted 'MEZ' in common
+ usage.
- Use a consistent style in a zone's history. For example, if a zone's
- history tends to use numeric abbreviations and a particular
- entry could go either way, use a numeric abbreviation.
+ Use a consistent style in a tz region's history.
+ For example, if history tends to use numeric
+ abbreviations and a particular entry could go either way, use a
+ numeric abbreviation.
- Use UT (with time zone abbreviation '-00') for
- locations while uninhabited. The leading
- '-' is a flag that the time
- zone is in some sense undefined; this notation is
- derived from Internet RFC 3339.
+ Use
+ Universal Time
+ (UT) (with time zone abbreviation '-00') for
+ locations while uninhabited.
+ The leading '-' is a flag that the UT offset is in
+ some sense undefined; this notation is derived
+ from Internet
+ RFC 3339.
+
Application writers should note that these abbreviations are ambiguous
in practice: e.g., 'CST' means one thing in China and something else
in North America, and 'IST' can refer to time in India, Ireland or
-Israel. To avoid ambiguity, use numeric UT offsets like
+Israel.
+To avoid ambiguity, use numeric UT offsets like
'-0600' instead of time zone abbreviations like 'CST'.
-
-
+
-
-
Accuracy of the tz database
+
+
Accuracy of the tz database
-The tz database is not authoritative, and it surely has errors.
+The tz database is not authoritative, and it
+surely has errors.
Corrections are welcome and encouraged; see the file CONTRIBUTING.
Users requiring authoritative data should consult national standards
bodies and the references cited in the database's comments.
-Errors in the tz database arise from many sources:
+Errors in the tz database arise from many sources:
+
- The tz database predicts future timestamps, and current predictions
- will be incorrect after future governments change the rules.
- For example, if today someone schedules a meeting for 13:00 next
- October 1, Casablanca time, and tomorrow Morocco changes its
- daylight saving rules, software can mess up after the rule change
- if it blithely relies on conversions made before the change.
-
-
- The pre-1970 entries in this database cover only a tiny sliver of how
- clocks actually behaved; the vast majority of the necessary
- information was lost or never recorded. Thousands more zones would
- be needed if the tz database's scope were extended to cover even
- just the known or guessed history of standard time; for example,
- the current single entry for France would need to split into dozens
- of entries, perhaps hundreds. And in most of the world even this
- approach would be misleading due to widespread disagreement or
- indifference about what times should be observed. In her 2015 book
- The Global Transformation of Time, 1870-1950, Vanessa Ogle writes
- "Outside of Europe and North America there was no system of time
- zones at all, often not even a stable landscape of mean times,
- prior to the middle decades of the twentieth century". See:
- Timothy Shenk, Booked:
- A Global History of Time. Dissent 2015-12-17.
-
-
- Most of the pre-1970 data entries come from unreliable sources, often
- astrology books that lack citations and whose compilers evidently
- invented entries when the true facts were unknown, without
- reporting which entries were known and which were invented.
- These books often contradict each other or give implausible entries,
- and on the rare occasions when they are checked they are
- typically found to be incorrect.
-
-
- For the UK the tz database relies on years of first-class work done by
- Joseph Myers and others; see
- "History of
- legal time in Britain".
- Other countries are not done nearly as well.
-
-
- Sometimes, different people in the same city would maintain clocks
- that differed significantly. Railway time was used by railroad
- companies (which did not always agree with each other),
- church-clock time was used for birth certificates, etc.
- Often this was merely common practice, but sometimes it was set by law.
- For example, from 1891 to 1911 the UT offset in France was legally
- 0:09:21 outside train stations and 0:04:21 inside.
-
-
- Although a named location in the tz database stands for the
- containing region, its pre-1970 data entries are often accurate for
- only a small subset of that region. For example, Europe/London
- stands for the United Kingdom, but its pre-1847 times are valid
- only for locations that have London's exact meridian, and its 1847
- transition to GMT is known to be valid only for the L&NW and the
- Caledonian railways.
-
-
- The tz database does not record the earliest time for which a zone's
- data entries are thereafter valid for every location in the region.
- For example, Europe/London is valid for all locations in its
- region after GMT was made the standard time, but the date of
- standardization (1880-08-02) is not in the tz database, other than
- in commentary. For many zones the earliest time of validity is
- unknown.
-
-
- The tz database does not record a region's boundaries, and in many
- cases the boundaries are not known. For example, the zone
- America/Kentucky/Louisville represents a region around
- the city of
- Louisville, the boundaries of which are unclear.
-
-
- Changes that are modeled as instantaneous transitions in the tz
- database were often spread out over hours, days, or even decades.
-
-
- Even if the time is specified by law, locations sometimes
- deliberately flout the law.
-
-
- Early timekeeping practices, even assuming perfect clocks, were
- often not specified to the accuracy that the tz database requires.
-
-
- Sometimes historical timekeeping was specified more precisely
- than what the tz database can handle. For example, from 1909 to
- 1937 Netherlands clocks were legally UT +00:19:32.13, but the tz
- database cannot represent the fractional second.
-
-
- Even when all the timestamp transitions recorded by the tz database
- are correct, the tz rules that generate them may not faithfully
- reflect the historical rules. For example, from 1922 until World
- War II the UK moved clocks forward the day following the third
- Saturday in April unless that was Easter, in which case it moved
- clocks forward the previous Sunday. Because the tz database has no
- way to specify Easter, these exceptional years are entered as
- separate tz Rule lines, even though the legal rules did not change.
-
-
- The tz database models pre-standard time using the proleptic Gregorian
- calendar and local mean time (LMT), but many people used other
- calendars and other timescales. For example, the Roman Empire used
- the Julian calendar, and had 12 varying-length daytime hours with a
- non-hour-based system at night.
-
-
- Early clocks were less reliable, and data entries do not represent
- clock error.
-
-
- The tz database assumes Universal Time (UT) as an origin, even
- though UT is not standardized for older timestamps. In the tz
- database commentary, UT denotes a family of time standards that
- includes Coordinated Universal Time (UTC) along with other variants
- such as UT1 and GMT, with days starting at midnight. Although UT
- equals UTC for modern timestamps, UTC was not defined until 1960,
- so commentary uses the more-general abbreviation UT for timestamps
- that might predate 1960. Since UT, UT1, etc. disagree slightly,
- and since pre-1972 UTC seconds varied in length, interpretation of
- older timestamps can be problematic when subsecond accuracy is
- needed.
-
-
- Civil time was not based on atomic time before 1972, and we don't
- know the history of earth's rotation accurately enough to map SI
- seconds to historical solar time to more than about one-hour
- accuracy. See: Stephenson FR, Morrison LV, Hohenkerk CY.
- Measurement
- of the Earth's rotation: 720 BC to AD 2015.
- Proc Royal Soc A. 2016 Dec 7;472:20160404.
- Also see: Espenak F. Uncertainty
- in Delta T (ÎT).
-
-
- The relationship between POSIX time (that is, UTC but ignoring leap
- seconds) and UTC is not agreed upon after 1972. Although the POSIX
- clock officially stops during an inserted leap second, at least one
- proposed standard has it jumping back a second instead; and in
- practice POSIX clocks more typically either progress glacially during
- a leap second, or are slightly slowed while near a leap second.
-
-
- The tz database does not represent how uncertain its information is.
- Ideally it would contain information about when data entries are
- incomplete or dicey. Partial temporal knowledge is a field of
- active research, though, and it's not clear how to apply it here.
+ The tz database predicts future
+ timestamps, and current predictions
+ will be incorrect after future governments change the rules.
+ For example, if today someone schedules a meeting for 13:00 next
+ October 1, Casablanca time, and tomorrow Morocco changes its
+ daylight saving rules, software can mess up after the rule change
+ if it blithely relies on conversions made before the change.
+
+
+ The pre-1970 entries in this database cover only a tiny sliver of how
+ clocks actually behaved; the vast majority of the necessary
+ information was lost or never recorded.
+ Thousands more tz regions would be needed if
+ the tz database's scope were extended to
+ cover even just the known or guessed history of standard time; for
+ example, the current single entry for France would need to split
+ into dozens of entries, perhaps hundreds.
+ And in most of the world even this approach would be misleading
+ due to widespread disagreement or indifference about what times
+ should be observed.
+ In her 2015 book
+ The
+ Global Transformation of Time, 1870–1950,
+ Vanessa Ogle writes
+ "Outside of Europe and North America there was no system of time
+ zones at all, often not even a stable landscape of mean times,
+ prior to the middle decades of the twentieth century".
+ See: Timothy Shenk, Booked:
+ A Global History of Time. Dissent 2015-12-17.
+
+
+ Most of the pre-1970 data entries come from unreliable sources, often
+ astrology books that lack citations and whose compilers evidently
+ invented entries when the true facts were unknown, without
+ reporting which entries were known and which were invented.
+ These books often contradict each other or give implausible entries,
+ and on the rare occasions when they are checked they are
+ typically found to be incorrect.
+
+
+ For the UK the tz database relies on
+ years of first-class work done by
+ Joseph Myers and others; see
+ "History of
+ legal time in Britain".
+ Other countries are not done nearly as well.
+
+
+ Sometimes, different people in the same city maintain clocks
+ that differ significantly.
+ Historically, railway time was used by railroad companies (which
+ did not always
+ agree with each other), church-clock time was used for birth
+ certificates, etc.
+ More recently, competing political groups might disagree about
+ clock settings. Often this is merely common practice, but
+ sometimes it is set by law.
+ For example, from 1891 to 1911 the UT offset in France
+ was legally UT +00:09:21 outside train stations and
+ UT +00:04:21 inside. Other examples include
+ Chillicothe in 1920, Palm Springs in 1946/7, and Jerusalem and
+ Ãrümqi to this day.
+
+
+ Although a named location in the tz
+ database stands for the containing region, its pre-1970 data
+ entries are often accurate for only a small subset of that region.
+ For example, Europe/London stands for the United
+ Kingdom, but its pre-1847 times are valid only for locations that
+ have London's exact meridian, and its 1847 transition
+ to GMT is known to be valid only for the L&NW and
+ the Caledonian railways.
+
+
+ The tz database does not record the
+ earliest time for which a tz region's
+ data entries are thereafter valid for every location in the region.
+ For example, Europe/London is valid for all locations
+ in its region after GMT was made the standard time,
+ but the date of standardization (1880-08-02) is not in the
+ tz database, other than in commentary.
+ For many tz regions the earliest time of
+ validity is unknown.
+
+
+ The tz database does not record a
+ region's boundaries, and in many cases the boundaries are not known.
+ For example, the tz region
+ America/Kentucky/Louisville represents a region
+ around the city of Louisville, the boundaries of which are
+ unclear.
+
+
+ Changes that are modeled as instantaneous transitions in the
+ tz
+ database were often spread out over hours, days, or even decades.
+
+
+ Even if the time is specified by law, locations sometimes
+ deliberately flout the law.
+
+
+ Early timekeeping practices, even assuming perfect clocks, were
+ often not specified to the accuracy that the
+ tz database requires.
+
+
+ Sometimes historical timekeeping was specified more precisely
+ than what the tz code can handle.
+ For example, from 1909 to 1937 Netherlands clocks were legally Amsterdam Mean
+ Time (estimated to be UT
+ +00:19:32.13), but the tz
+ code cannot represent the fractional second.
+ In practice these old specifications were rarely if ever
+ implemented to subsecond precision.
+
+
+ Even when all the timestamp transitions recorded by the
+ tz database are correct, the
+ tz rules that generate them may not
+ faithfully reflect the historical rules.
+ For example, from 1922 until World War II the UK moved clocks
+ forward the day following the third Saturday in April unless that
+ was Easter, in which case it moved clocks forward the previous
+ Sunday.
+ Because the tz database has no
+ way to specify Easter, these exceptional years are entered as
+ separate tz Rule lines, even though the
+ legal rules did not change.
+
+
+ The tz database models pre-standard time
+ using the proleptic
+ Gregorian calendar and local mean time, but many people used
+ other calendars and other timescales.
+ For example, the Roman Empire used
+ the Julian
+ calendar,
+ and Roman
+ timekeeping had twelve varying-length daytime hours with a
+ non-hour-based system at night.
+
+
+ Early clocks were less reliable, and data entries do not represent
+ clock error.
+
+
+ The tz database assumes Universal Time
+ (UT) as an origin, even though UT is not
+ standardized for older timestamps.
+ In the tz database commentary,
+ UT denotes a family of time standards that includes
+ Coordinated Universal Time (UTC) along with other
+ variants such as UT1 and GMT,
+ with days starting at midnight.
+ Although UT equals UTC for modern
+ timestamps, UTC was not defined until 1960, so
+ commentary uses the more-general abbreviation UT for
+ timestamps that might predate 1960.
+ Since UT, UT1, etc. disagree slightly,
+ and since pre-1972 UTC seconds varied in length,
+ interpretation of older timestamps can be problematic when
+ subsecond accuracy is needed.
+
+ The relationship between POSIX time (that is, UTC but
+ ignoring leap
+ seconds) and UTC is not agreed upon after 1972.
+ Although the POSIX
+ clock officially stops during an inserted leap second, at least one
+ proposed standard has it jumping back a second instead; and in
+ practice POSIX clocks more typically either progress glacially during
+ a leap second, or are slightly slowed while near a leap second.
+
+
+ The tz database does not represent how
+ uncertain its information is.
+ Ideally it would contain information about when data entries are
+ incomplete or dicey.
+ Partial temporal knowledge is a field of active research, though,
+ and it is not clear how to apply it here.
-
-In short, many, perhaps most, of the tz database's pre-1970 and future
-timestamps are either wrong or misleading. Any attempt to pass the
-tz database off as the definition of time should be unacceptable to
-anybody who cares about the facts. In particular, the tz database's
-LMT offsets should not be considered meaningful, and should not prompt
-creation of zones merely because two locations differ in LMT or
-transitioned to standard time at different dates.
-
-
-
-
-
Time and date functions
-The tz code contains time and date functions that are upwards
-compatible with those of POSIX.
+In short, many, perhaps most, of the tz
+database's pre-1970 and future timestamps are either wrong or
+misleading.
+Any attempt to pass the
+tz database off as the definition of time
+should be unacceptable to anybody who cares about the facts.
+In particular, the tz database's
+LMT offsets should not be considered meaningful, and
+should not prompt creation of tz regions
+merely because two locations
+differ in LMT or transitioned to standard time at
+different dates.
+
+
+
Time and date functions
-POSIX has the following properties and limitations.
+The tz code contains time and date functions
+that are upwards compatible with those of POSIX.
+Code compatible with this package is already
+part of many platforms, where the
+primary use of this package is to update obsolete time-related files.
+To do this, you may need to compile the time zone compiler
+'zic' supplied with this package instead of using the
+system 'zic', since the format of zic's
+input is occasionally extended, and a platform may still be shipping
+an older zic.
+
+
POSIX properties and limitations
- In POSIX, time display in a process is controlled by the
- environment variable TZ. Unfortunately, the POSIX TZ string takes
- a form that is hard to describe and is error-prone in practice.
- Also, POSIX TZ strings can't deal with other (for example, Israeli)
- daylight saving time rules, or situations where more than two
- time zone abbreviations are used in an area.
+ In POSIX, time display in a process is controlled by the
+ environment variable TZ.
+ Unfortunately, the POSIX
+ TZ string takes a form that is hard to describe and
+ is error-prone in practice.
+ Also, POSIX TZ strings cannot deal with daylight
+ saving time rules not based on the Gregorian calendar (as in
+ Iran), or with situations where more than two time zone
+ abbreviations or UT offsets are used in an area.
+
- The POSIX TZ string takes the following form:
+ The POSIX TZ string takes the following form:
- are 3 or more characters specifying the standard
- and daylight saving time (DST) zone names.
- Starting with POSIX.1-2001, std
- and dst may also be
- in a quoted form like '<+09>'; this allows
- "+" and "-" in the names.
+ are 3 or more characters specifying the standard
+ and daylight saving time (DST) zone names.
+ Starting with POSIX.1-2001, std and dst
+ may also be in a quoted form like '<+09>';
+ this allows "+" and "-" in the names.
offset
- is of the form
- '[±]hh:[mm[:ss]]'
- and specifies the offset west of UT. 'hh'
- may be a single digit; 0≤hh≤24.
- The default DST offset is one hour ahead of standard time.
+ is of the form
+ '[±]hh:[mm[:ss]]'
+ and specifies the offset west of UT.
+ 'hh' may be a single digit;
+ 0≤hh≤24.
+ The default DST offset is one hour ahead of
+ standard time.
date[/time],date[/time]
- specifies the beginning and end of DST. If this is absent,
- the system supplies its own rules for DST, and these can
- differ from year to year; typically US DST rules are used.
+ specifies the beginning and end of DST.
+ If this is absent, the system supplies its own ruleset
+ for DST, and its rules can differ from year to year;
+ typically US DST rules are used.
time
- takes the form
- 'hh:[mm[:ss]]'
- and defaults to 02:00.
- This is the same format as the offset, except that a
- leading '+' or '-' is not allowed.
+ takes the form
+ 'hh:[mm[:ss]]'
+ and defaults to 02:00.
+ This is the same format as the offset, except that a
+ leading '+' or '-' is not allowed.
date
- takes one of the following forms:
+ takes one of the following forms:
Jn (1≤n≤365)
- origin-1 day number not counting February 29
-
+ origin-1 day number not counting February 29
+
n (0≤n≤365)
- origin-0 day number counting February 29 if present
-
-
Mm.n.d (0[Sunday]≤d≤6[Saturday], 1≤n≤5, 1≤m≤12)
- for the dth day of
- week n of month m of the
- year, where week 1 is the first week in which
- day d appears, and '5'
- stands for the last week in which
- day d appears
- (which may be either the 4th or 5th week).
- Typically, this is the only useful form;
- the n
- and Jn forms are
- rarely used.
+ origin-0 day number counting February 29 if present
+
+ for the dth day of week n of
+ month m of the year, where week 1 is the first
+ week in which day d appears, and
+ '5' stands for the last week in which
+ day d appears (which may be either the 4th or
+ 5th week).
+ Typically, this is the only useful form; the n
+ and Jn forms are rarely used.
-
-
-
- Here is an example POSIX TZ string for New Zealand after 2007.
- It says that standard time (NZST) is 12 hours ahead of UT,
- and that daylight saving time (NZDT) is observed from September's
- last Sunday at 02:00 until April's first Sunday at 03:00:
+
+
+
-
TZ='NZST-12NZDT,M9.5.0,M4.1.0/3'
+
+ Here is an example POSIX TZ string for New
+ Zealand after 2007.
+ It says that standard time (NZST) is 12 hours ahead
+ of UT, and that daylight saving time
+ (NZDT) is observed from September's last Sunday at
+ 02:00 until April's first Sunday at 03:00:
+
+
+
TZ='NZST-12NZDT,M9.5.0,M4.1.0/3'
+
+
+ This POSIX TZ string is hard to remember, and
+ mishandles some timestamps before 2008.
+ With this package you can use this instead:
+
- This POSIX TZ string is hard to remember, and mishandles some
- timestamps before 2008. With this package you can use this
- instead:
+
TZ='Pacific/Auckland'
+
+
+ POSIX does not define the exact meaning of TZ values like
+ "EST5EDT".
+ Typically the current US DST rules
+ are used to interpret such values, but this means that the
+ US DST rules are compiled into each
+ program that does time conversion.
+ This means that when
+ US time conversion rules change (as in the United
+ States in 1987), all programs that do time conversion must be
+ recompiled to ensure proper results.
+
+
+ The TZ environment variable is process-global, which
+ makes it hard to write efficient, thread-safe applications that
+ need access to multiple time zone rulesets.
+
+
+ In POSIX, there is no tamper-proof way for a process to learn the
+ system's best idea of local wall clock.
+ (This is important for applications that an administrator wants
+ used only at certain times – without regard to whether the
+ user has fiddled the
+ TZ environment variable.
+ While an administrator can "do everything in UT" to
+ get around the problem, doing so is inconvenient and precludes
+ handling daylight saving time shifts - as might be required to
+ limit phone calls to off-peak hours.)
+
+
+ POSIX provides no convenient and efficient way to determine
+ the UT offset and time zone abbreviation of arbitrary
+ timestamps, particularly for tz regions
+ that do not fit into the POSIX model.
+
+
+ POSIX requires that systems ignore leap seconds.
+
+
+ The tz code attempts to support all the
+ time_t implementations allowed by POSIX.
+ The time_t type represents a nonnegative count of seconds
+ since 1970-01-01 00:00:00 UTC, ignoring leap seconds.
+ In practice, time_t is usually a signed 64- or 32-bit
+ integer; 32-bit signed time_t values stop working after
+ 2038-01-19 03:14:07 UTC, so new implementations these
+ days typically use a signed 64-bit integer.
+ Unsigned 32-bit integers are used on one or two platforms, and 36-bit
+ and 40-bit integers are also used occasionally.
+ Although earlier POSIX versions allowed time_t to be a
+ floating-point type, this was not supported by any practical systems,
+ and POSIX.1-2013 and the tz code both
+ require time_t to be an integer type.
+
+
-
TZ='Pacific/Auckland'
+
Extensions to POSIX in the
+tz code
+
+
+
+ The TZ environment variable is used in generating
+ the name of a binary file from which time-related information is read
+ (or is interpreted à la POSIX); TZ is no longer
+ constrained to be a three-letter time zone
+ abbreviation followed by a number of hours and an optional three-letter
+ daylight time zone abbreviation.
+ The daylight saving time rules to be used for a
+ particular tz region are encoded in the
+ binary file; the format of the file
+ allows U.S., Australian, and other rules to be encoded, and
+ allows for situations where more than two time zone
+ abbreviations are used.
+
+
+ It was recognized that allowing the TZ environment
+ variable to take on values such as 'America/New_York'
+ might cause "old" programs (that expect TZ to have a
+ certain form) to operate incorrectly; consideration was given to using
+ some other environment variable (for example, TIMEZONE)
+ to hold the string used to generate the binary file's name.
+ In the end, however, it was decided to continue using
+ TZ: it is widely used for time zone purposes;
+ separately maintaining both TZ
+ and TIMEZONE seemed a nuisance; and systems where
+ "new" forms of TZ might cause problems can simply
+ use TZ values such as "EST5EDT" which
+ can be used both by "new" programs (Ã la POSIX) and "old"
+ programs (as zone names and offsets).
+
- POSIX does not define the exact meaning of TZ values like
- "EST5EDT".
- Typically the current US DST rules are used to interpret such values,
- but this means that the US DST rules are compiled into each program
- that does time conversion. This means that when US time conversion
- rules change (as in the United States in 1987), all programs that
- do time conversion must be recompiled to ensure proper results.
+ The code supports platforms with a UT offset member
+ in struct tm, e.g., tm_gmtoff.
- The TZ environment variable is process-global, which makes it hard
- to write efficient, thread-safe applications that need access
- to multiple time zones.
+ The code supports platforms with a time zone abbreviation member in
+ struct tm, e.g., tm_zone.
- In POSIX, there's no tamper-proof way for a process to learn the
- system's best idea of local wall clock. (This is important for
- applications that an administrator wants used only at certain
- times –
- without regard to whether the user has fiddled the TZ environment
- variable. While an administrator can "do everything in UT" to get
- around the problem, doing so is inconvenient and precludes handling
- daylight saving time shifts - as might be required to limit phone
- calls to off-peak hours.)
+ Functions tzalloc, tzfree,
+ localtime_rz, and mktime_z for
+ more-efficient thread-safe applications that need to use multiple
+ time zone rulesets.
+ The tzalloc and tzfree functions
+ allocate and free objects of type timezone_t,
+ and localtime_rz and mktime_z are
+ like localtime_r and mktime with an
+ extra timezone_t argument.
+ The functions were inspired by NetBSD.
- POSIX provides no convenient and efficient way to determine the UT
- offset and time zone abbreviation of arbitrary timestamps,
- particularly for time zone settings that do not fit into the
- POSIX model.
+ A function tzsetwall has been added to arrange for the
+ system's best approximation to local wall clock time to be delivered
+ by subsequent calls to localtime.
+ Source code for portable applications that "must" run on local wall
+ clock time should call tzsetwall;
+ if such code is moved to "old" systems that do not
+ provide tzsetwall, you will not be able to generate an
+ executable program.
+ (These functions also arrange for local wall clock time to
+ be used if tzset is called – directly or
+ indirectly – and there is no TZ environment
+ variable; portable applications should not, however, rely on this
+ behavior since it is not the way SVR2
+ systems behave.)
- POSIX requires that systems ignore leap seconds.
+ Negative time_t values are supported, on systems
+ where time_t is signed.
- The tz code attempts to support all the time_t
- implementations allowed by POSIX. The time_t
- type represents a nonnegative count of
- seconds since 1970-01-01 00:00:00 UTC, ignoring leap seconds.
- In practice, time_t is usually a signed 64- or
- 32-bit integer; 32-bit signed time_t values stop
- working after 2038-01-19 03:14:07 UTC, so
- new implementations these days typically use a signed 64-bit integer.
- Unsigned 32-bit integers are used on one or two platforms,
- and 36-bit and 40-bit integers are also used occasionally.
- Although earlier POSIX versions allowed time_t to be a
- floating-point type, this was not supported by any practical
- systems, and POSIX.1-2013 and the tz code both
- require time_t
- to be an integer type.
+ These functions can account for leap seconds, thanks to Bradley White.
+
+
POSIX features no longer needed
-These are the extensions that have been made to the POSIX functions:
+POSIX and ISO C
+define some APIs that are vestigial:
+they are not needed, and are relics of a too-simple model that does
+not suffice to handle many real-world timestamps.
+Although the tz code supports these
+vestigial APIs for backwards compatibility, they should
+be avoided in portable applications.
+The vestigial APIs are:
-
- The TZ environment variable is used in generating the name of a file
- from which time zone information is read (or is interpreted a la
- POSIX); TZ is no longer constrained to be a three-letter time zone
- name followed by a number of hours and an optional three-letter
- daylight time zone name. The daylight saving time rules to be used
- for a particular time zone are encoded in the time zone file;
- the format of the file allows U.S., Australian, and other rules to be
- encoded, and allows for situations where more than two time zone
- abbreviations are used.
-
-
- It was recognized that allowing the TZ environment variable to
- take on values such as 'America/New_York' might
- cause "old" programs
- (that expect TZ to have a certain form) to operate incorrectly;
- consideration was given to using some other environment variable
- (for example, TIMEZONE) to hold the string used to generate the
- time zone information file name. In the end, however, it was decided
- to continue using TZ: it is widely used for time zone purposes;
- separately maintaining both TZ and TIMEZONE seemed a nuisance;
- and systems where "new" forms of TZ might cause problems can simply
- use TZ values such as "EST5EDT" which can be used both by
- "new" programs (a la POSIX) and "old" programs (as zone names and
- offsets).
-
-
-
- The code supports platforms with a UT offset member
- in struct tm,
- e.g., tm_gmtoff.
-
-
- The code supports platforms with a time zone abbreviation member in
- struct tm, e.g., tm_zone.
-
-
- Since the TZ environment variable can now be used to control time
- conversion, the daylight
- and timezone variables are no longer needed.
- (These variables are defined and set by tzset;
- however, their values will not be used
- by localtime.)
-
-
- Functions tzalloc, tzfree,
- localtime_rz, and mktime_z for
- more-efficient thread-safe applications that need to use
- multiple time zones. The tzalloc
- and tzfree functions allocate and free objects of
- type timezone_t, and localtime_rz
- and mktime_z are like localtime_r
- and mktime with an extra
- timezone_t argument. The functions were inspired
- by NetBSD.
-
-
- A function tzsetwall has been added to arrange
- for the system's
- best approximation to local wall clock time to be delivered by
- subsequent calls to localtime. Source code for portable
- applications that "must" run on local wall clock time should call
- tzsetwall; if such code is moved to "old" systems that don't
- provide tzsetwall, you won't be able to generate an executable program.
- (These time zone functions also arrange for local wall clock time to be
- used if tzset is called – directly or indirectly –
- and there's no TZ
- environment variable; portable applications should not, however, rely
- on this behavior since it's not the way SVR2 systems behave.)
-
-
- Negative time_t values are supported, on systems
- where time_t is signed.
-
-
- These functions can account for leap seconds, thanks to Bradley White.
-
+ The POSIX tzname variable does not suffice and is no
+ longer needed.
+ To get a timestamp's time zone abbreviation, consult
+ the tm_zone member if available; otherwise,
+ use strftime's "%Z" conversion
+ specification.
+
+
+ The POSIX daylight and timezone
+ variables do not suffice and are no longer needed.
+ To get a timestamp's UT offset, consult
+ the tm_gmtoff member if available; otherwise,
+ subtract values returned by localtime
+ and gmtime using the rules of the Gregorian calendar,
+ or use strftime's "%z" conversion
+ specification if a string like "+0900" suffices.
+
+
+ The tm_isdst member is almost never needed and most of
+ its uses should be discouraged in favor of the abovementioned
+ APIs.
+ Although it can still be used in arguments to
+ mktime to disambiguate timestamps near
+ a DST transition when the clock jumps back, this
+ disambiguation does not work when standard time itself jumps back,
+ which can occur when a location changes to a time zone with a
+ lesser UT offset.
+
-
-Points of interest to folks with other systems:
-
+
+
Other portability notes
- Code compatible with this package is already part of many platforms,
- including GNU/Linux, Android, the BSDs, Chromium OS, Cygwin, AIX, iOS,
- BlackBery 10, macOS, Microsoft Windows, OpenVMS, and Solaris.
- On such hosts, the primary use of this package
- is to update obsolete time zone rule tables.
- To do this, you may need to compile the time zone compiler
- 'zic' supplied with this package instead of using
- the system 'zic', since the format
- of zic's input is occasionally extended, and a
- platform may still be shipping an older zic.
-
-
- The UNIX Version 7 timezone function is not
- present in this package;
- it's impossible to reliably map timezone's arguments (a "minutes west
- of GMT" value and a "daylight saving time in effect" flag) to a
- time zone abbreviation, and we refuse to guess.
- Programs that in the past used the timezone function may now examine
- localtime(&clock)->tm_zone
- (if TM_ZONE is defined) or
- tzname[localtime(&clock)->tm_isdst]
- (if HAVE_TZNAME is defined)
- to learn the correct time zone abbreviation to use.
-
-
- The 4.2BSD gettimeofday function is not used in
- this package.
- This formerly let users obtain the current UTC offset and DST flag,
- but this functionality was removed in later versions of BSD.
-
-
- In SVR2, time conversion fails for near-minimum or near-maximum
- time_t values when doing conversions for places
- that don't use UT.
- This package takes care to do these conversions correctly.
- A comment in the source code tells how to get compatibly wrong
- results.
+ The 7th Edition
+ UNIXtimezone function is not present in this
+ package; it is impossible to reliably map timezone's
+ arguments (a "minutes west of GMT" value and a
+ "daylight saving time in effect" flag) to a time zone
+ abbreviation, and we refuse to guess.
+ Programs that in the past used the timezone function
+ may now examine localtime(&clock)->tm_zone
+ (if TM_ZONE is defined) or
+ tzname[localtime(&clock)->tm_isdst]
+ (if HAVE_TZNAME is defined) to learn the correct time
+ zone abbreviation to use.
+
+
+ The 4.2BSD
+ gettimeofday function is not
+ used in this package.
+ This formerly let users obtain the current UTC offset
+ and DST flag, but this functionality was removed in
+ later versions of BSD.
+
+
+ In SVR2, time conversion fails for near-minimum or
+ near-maximum time_t values when doing conversions
+ for places that do not use UT.
+ This package takes care to do these conversions correctly.
+ A comment in the source code tells how to get compatibly wrong
+ results.
+
+
+ The functions that are conditionally compiled
+ if STD_INSPIRED is defined should, at this point, be
+ looked on primarily as food for thought.
+ They are not in any sense "standard compatible" – some are
+ not, in fact, specified in any standard.
+ They do, however, represent responses of various authors to
+ standardization proposals.
+
+
+ Other time conversion proposals, in particular the one developed
+ by folks at Hewlett Packard, offer a wider selection of functions
+ that provide capabilities beyond those provided here.
+ The absence of such functions from this package is not meant to
+ discourage the development, standardization, or use of such
+ functions.
+ Rather, their absence reflects the decision to make this package
+ contain valid extensions to POSIX, to ensure its broad
+ acceptability.
+ If more powerful time conversion functions can be standardized, so
+ much the better.
-
-The functions that are conditionally compiled
-if STD_INSPIRED is defined
-should, at this point, be looked on primarily as food for thought. They are
-not in any sense "standard compatible" – some are not, in fact,
-specified in any standard. They do, however, represent responses of
-various authors to
-standardization proposals.
-
+
+
+
Interface stability
-Other time conversion proposals, in particular the one developed by folks at
-Hewlett Packard, offer a wider selection of functions that provide capabilities
-beyond those provided here. The absence of such functions from this package
-is not meant to discourage the development, standardization, or use of such
-functions. Rather, their absence reflects the decision to make this package
-contain valid extensions to POSIX, to ensure its broad acceptability. If
-more powerful time conversion functions can be standardized, so much the
-better.
+The tz code and data supply the following interfaces:
-
-
-
-
Interface stability
-
-The tz code and data supply the following interfaces:
-
- The programs tzselect, zdump,
- and zic, documented in their man pages.
+ The programs tzselect, zdump,
+ and zic, documented in their man pages.
- The format of zic input files, documented in
- the zic man page.
+ The format of zic input files, documented in
+ the zic man page.
- The format of zic output files, documented in
- the tzfile man page.
+ The format of zic output files, documented in
+ the tzfile man page.
- The format of zone table files, documented in zone1970.tab.
+ The format of zone table files, documented in zone1970.tab.
- The format of the country code file, documented in iso3166.tab.
+ The format of the country code file, documented in iso3166.tab.
- The version number of the code and data, as the first line of
- the text file 'version' in each release.
+ The version number of the code and data, as the first line of
+ the text file 'version' in each release.
+
Interface changes in a release attempt to preserve compatibility with
-recent releases. For example, tz data files typically do not rely on
-recently-added zic features, so that users can run
-older zic versions to process newer data
-files. Sources for time zone and daylight
-saving time data describes how
-releases are tagged and distributed.
+recent releases.
+For example, tz data files typically do not
+rely on recently-added zic features, so that users can
+run older zic versions to process newer data files.
+Downloading
+the tz database describes how releases
+are tagged and distributed.
-Interfaces not listed above are less stable. For example, users
-should not rely on particular UT offsets or abbreviations for
-timestamps, as data entries are often based on guesswork and these
-guesses may be corrected or improved.
+Interfaces not listed above are less stable.
+For example, users should not rely on particular UT
+offsets or abbreviations for timestamps, as data entries are often
+based on guesswork and these guesses may be corrected or improved.
-
+
-
-
-
Calendrical issues
+
+
Calendrical issues
Calendrical issues are a bit out of scope for a time zone database,
but they indicate the sort of problems that we would run into if we
-extended the time zone database further into the past. An excellent
-resource in this area is Nachum Dershowitz and Edward M. Reingold,
-Calendrical
-Calculations: Third Edition, Cambridge University Press (2008).
-Other information and sources are given in the file 'calendars'
-in the tz distribution. They sometimes disagree.
+extended the time zone database further into the past.
+An excellent resource in this area is Edward M. Reingold
+and Nachum Dershowitz, Calendrical
+Calculations: The Ultimate Edition, Cambridge University Press (2018).
+Other information and sources are given in the file 'calendars'
+in the tz distribution.
+They sometimes disagree.
-
-
+
-
-
Time and time zones on other planets
+
+
Time and time zones on other planets
-Some people's work schedules use Mars time. Jet Propulsion Laboratory
-(JPL) coordinators have kept Mars time on and off at least since 1997
-for the Mars Pathfinder mission. Some of their family members have
-also adapted to Mars time. Dozens of special Mars watches were built
-for JPL workers who kept Mars time during the Mars Exploration
-Rovers mission (2004). These timepieces look like normal Seikos and
-Citizens but use Mars seconds rather than terrestrial seconds.
+Some people's work schedules
+use Mars time.
+Jet Propulsion Laboratory (JPL) coordinators kept Mars time on
+and off during the
+Mars
+Pathfinder mission.
+Some of their family members also adapted to Mars time.
+Dozens of special Mars watches were built for JPL workers who kept
+Mars time during the Mars Exploration Rovers mission (2004).
+These timepieces look like normal Seikos and Citizens but use Mars
+seconds rather than terrestrial seconds.
A Mars solar day is called a "sol" and has a mean period equal to
-about 24 hours 39 minutes 35.244 seconds in terrestrial time. It is
-divided into a conventional 24-hour clock, so each Mars second equals
-about 1.02749125 terrestrial seconds.
+about 24 hours 39 minutes 35.244 seconds in terrestrial time.
+It is divided into a conventional 24-hour clock, so each Mars second
+equals about 1.02749125 terrestrial seconds.
-The prime meridian of Mars goes through the center of the crater
-Airy-0, named in honor of the British astronomer who built the
-Greenwich telescope that defines Earth's prime meridian. Mean solar
-time on the Mars prime meridian is called Mars Coordinated Time (MTC).
+The prime
+meridian of Mars goes through the center of the crater
+Airy-0, named in
+honor of the British astronomer who built the Greenwich telescope that
+defines Earth's prime meridian.
+Mean solar time on the Mars prime meridian is
+called Mars
+Coordinated Time (MTC).
Each landed mission on Mars has adopted a different reference for
solar time keeping, so there is no real standard for Mars time zones.
-For example, the Mars Exploration Rover project (2004) defined two
-time zones "Local Solar Time A" and "Local Solar Time B" for its two
-missions, each zone designed so that its time equals local true solar
-time at approximately the middle of the nominal mission. Such a "time
-zone" is not particularly suited for any application other than the
-mission itself.
+For example, the
+Mars
+Exploration Rover project (2004) defined two time zones "Local
+Solar Time A" and "Local Solar Time B" for its two missions, each zone
+designed so that its time equals local true solar time at
+approximately the middle of the nominal mission.
+Such a "time zone" is not particularly suited for any application
+other than the mission itself.
Many calendars have been proposed for Mars, but none have achieved
-wide acceptance. Astronomers often use Mars Sol Date (MSD) which is a
+wide acceptance.
+Astronomers often use Mars Sol Date (MSD) which is a
sequential count of Mars solar days elapsed since about 1873-12-29
-12:00 GMT.
+12:00 GMT.
In our solar system, Mars is the planet with time and calendar most
-like Earth's. On other planets, Sun-based time and calendars would
-work quite differently. For example, although Mercury's sidereal
-rotation period is 58.646 Earth days, Mercury revolves around the Sun
-so rapidly that an observer on Mercury's equator would see a sunrise
-only every 175.97 Earth days, i.e., a Mercury year is 0.5 of a Mercury
-day. Venus is more complicated, partly because its rotation is
-slightly retrograde: its year is 1.92 of its days. Gas giants like
-Jupiter are trickier still, as their polar and equatorial regions
-rotate at different rates, so that the length of a day depends on
-latitude. This effect is most pronounced on Neptune, where the day is
-about 12 hours at the poles and 18 hours at the equator.
+like Earth's.
+On other planets, Sun-based time and calendars would work quite
+differently.
+For example, although Mercury's
+sidereal
+rotation period is 58.646 Earth days, Mercury revolves around the
+Sun so rapidly that an observer on Mercury's equator would see a
+sunrise only every 175.97 Earth days, i.e., a Mercury year is 0.5 of a
+Mercury day.
+Venus is more complicated, partly because its rotation is slightly
+retrograde:
+its year is 1.92 of its days.
+Gas giants like Jupiter are trickier still, as their polar and
+equatorial regions rotate at different rates, so that the length of a
+day depends on latitude.
+This effect is most pronounced on Neptune, where the day is about 12
+hours at the poles and 18 hours at the equator.
-Although the tz database does not support time on other planets, it is
-documented here in the hopes that support will be added eventually.
+Although the tz database does not support
+time on other planets, it is documented here in the hopes that support
+will be added eventually.
-
+
-
+
diff --git a/tz-art.html b/tz-art.html
index 480b9e1..9624d8c 100644
--- a/tz-art.html
+++ b/tz-art.html
@@ -81,19 +81,19 @@ doing so got a crook trying to be declared dead to
emerge a bit too early from the titular enclosure.
-The 1960s ITC television series The Prisoner included an episode
-entitled "The Chimes of Big Ben" in which our protagonist tumbled to
+"The Chimes of Big Ben", The Prisoner, episode 2, ITC, 1967-10-06.
+Our protagonist tumbles to
the fraudulent nature of a Poland-to-England escape upon hearing "Big
Ben" chiming on Polish local time.
-The series Seinfeld included an episode entitled "The Susie," first
-broadcast 1997-02-13, in which Kramer decides that daylight saving time
+"The Susie", Seinfeld, season 8, episode 15, NBC, 1997-02-13.
+Kramer decides that daylight saving time
isn't coming fast enough, so he sets his watch ahead an hour.
-The "20 Hours in America" episode of The West Wing,
-first aired 2002-09-25, contained a The West Wing, season 4, episodes 1–2,
+2002-09-25, contained a scene that
saw White House staffers stranded in Indiana; they thought they had time to
catch Air Force One but were done in by intra-Indiana local time changes.
@@ -165,6 +165,11 @@ CBS, 2016-01-17.
The applicability of a contract hinges on the
time zone associated with a video timestamp.
+
+"Justice", Veep, season 6, episode 4, HBO, 2017-05-07.
+Jonah's inability to understand DST ends up impressing a wealthy
+backer who sets him up for a 2020 presidential run.
+
Sources for time zone and daylight saving time data
-Time zone and daylight saving rules are controlled by individual
+Time zone and
+daylight-saving
+rules are controlled by individual
governments. They are sometimes changed with little notice, and their
histories and planned futures are often recorded only fitfully. Here
is a summary of attempts to organize and record relevant data in this
@@ -20,12 +22,9 @@ time zone database contains code and data
that represent the history of local time
for many representative locations around the globe.
It is updated periodically to reflect changes made by political bodies
-to time zone
-boundaries and
-daylight-saving
-rules.
-This database (often called zoneinfo or
-tz)
+to time zone boundaries and daylight saving rules.
+This database (known as tz,
+tzdb, or zoneinfo)
is used by several implementations,
including
the
@@ -109,7 +108,7 @@ gzip -dc tzdata-latest.tar.gz | tar -xf -
release in a single-tarball format containing extra data
useful for regression testing:
These commands use convenience links to the latest release
of the tz database hosted by the
@@ -130,7 +129,7 @@ Since version 2016h, each release has contained a text file named
The releases are also available in an
FTP directory via a
-less-secure protocol .
+less-secure protocol.
Alternatively, a development repository of code and data can be
retrieved from GitHub via the shell
command:
@@ -182,6 +181,8 @@ data yourself. System-specific instructions for installing the
latest tz data have also been published
for AIX,
Android,
+ICU,
IBM
@@ -190,7 +191,7 @@ href="http://www.oracle.com/technetwork/java/javase/tzupdater-readme-136440.html
Java, Joda-Time, MySQL,
and Noda Time (see below).
+href="https://nodatime.org/userguide/tzdb">Noda Time (see below).
Sources for the tz database are
LF,
which can be modified by common text editors such
as GNU Emacs,
gedit, and
-vim.
+vim.
Specialized source-file editing can be done via the
Sublime
zoneinfo package for
Noda Time – Date and
time API for .NET
and TZ4Net
are similar to Joda-Time and Time4J, but for the .NET framework instead of
@@ -380,6 +384,11 @@ and a BSD-style license, respectively.
CompactTimeZoneGenerator
+compiles time zone data into a compact form designed for
+JavaScript. It is freely available under a combination of
+the MIT license and the Apache License.
Moment Timezone is a
plugin for the Moment.js date
manipulation library. It is freely available under the MIT
@@ -449,7 +458,7 @@ library that reads tz binary files and converts
time stamps from one time zone or format to another.
It is used by PHP,
-HHVM,
+HHVM,
and MongoDB.
It is freely available under the MIT license.
Time Zone
Master is a Microsoft Windows clock program that can automatically
download, compile and use tz releases. The Basic version
is free.
@@ -534,8 +543,8 @@ licenses to tz contributors.
Time-zone Atlas
is Astrodienst's Web version of Shanks and Pottenger's
time zone history atlases also published in software
-form by ACS-Starcrafts.
+href="https://astrocom.com/astrology-products/software/acs-atlas-software">software
+form by ACS-Starcrafts.
These atlases are extensive but unreliable, as Shanks appears to have
guessed many UT offsets and transitions. The atlases cite no
sources and do not indicate which entries are guesswork.
@@ -543,7 +552,7 @@ sources and do not indicate which entries are guesswork.
its own tztab(4) format.
Microsoft Windows has proprietary data mentioned
above.
World Time Zones
contains data from the Time Service Department of the
@@ -567,16 +576,16 @@ Library Map Collection
of the University of Texas at Austin has copies of
recent editions.
The pictorial quality is good,
-but the maps do not indicate summer time,
+but the maps do not indicate daylight saving time,
and parts of the data are a few years out of date.
The Oceanography, Hydrography, and Meteorology Service of the Uruguayan
+Navy (SOHMA) publishes an annual almanac
+(in Spanish).
Precision timekeeping
@@ -773,6 +790,8 @@ Time Zone Proceedings
lists changes to time zone boundaries.
href="http://leapsecond.com/hpan/an1289.pdf">The
Science of Timekeeping is a thorough introduction
to the theory and practice of precision timekeeping.
NTP: The Network
Time Protocol (Internet RFC 5905)
@@ -792,12 +811,12 @@ href="https://en.wikipedia.org/wiki/Dynamic_Host_Configuration_Protocol">D
option for a server to configure
a client's time zone and daylight saving settings automatically.
The IAU's ,
discussed further in
The
leap second: its history and possible future.
-UTC
+UTC
might be redefined
without Leap Seconds gives pointers on this
contentious issue, which was active until 2015 and could become active
@@ -857,7 +876,7 @@ zone names, abbreviations, identifiers, and formats. For example, it
contains French translations for "Eastern European Summer Time",
"EEST", and
"Bucharest". Its
-by-type
+by-type
charts show these values for many locales. Data values are available in
both LDML
(an XML format) and JSON.
diff --git a/tzfile.5 b/tzfile.5
index 3a4dd2b..530397f 100644
--- a/tzfile.5
+++ b/tzfile.5
@@ -173,7 +173,7 @@ For version-3-format time zone files, the POSIX-TZ-style string may
use two minor extensions to the POSIX TZ format, as described in
.BR newtzset (3).
First, the hours part of its transition times may be signed and range from
-\-167 through 167 instead of the POSIX-required unsigned values
+\*-167 through 167 instead of the POSIX-required unsigned values
from 0 through 24. Second, DST is in effect all year if it starts
January 1 at 00:00 and ends December 31 at 24:00 plus the difference
between daylight saving and standard time.
diff --git a/tzfile.5.txt b/tzfile.5.txt
index e6eb68e..d55ac47 100644
--- a/tzfile.5.txt
+++ b/tzfile.5.txt
@@ -116,7 +116,7 @@ DESCRIPTION
For version-3-format time zone files, the POSIX-TZ-style string may use
two minor extensions to the POSIX TZ format, as described in
newtzset(3). First, the hours part of its transition times may be
- signed and range from -167 through 167 instead of the POSIX-required
+ signed and range from 167 through 167 instead of the POSIX-required
unsigned values from 0 through 24. Second, DST is in effect all year
if it starts January 1 at 00:00 and ends December 31 at 24:00 plus the
difference between daylight saving and standard time.
diff --git a/version b/version
index f6a71fe..cc61cea 100644
--- a/version
+++ b/version
@@ -1 +1 @@
-2018c
+2018e
diff --git a/zdump.c b/zdump.c
index 60a027e..a4d9108 100644
--- a/zdump.c
+++ b/zdump.c
@@ -5,19 +5,9 @@
#include "version.h"
-/*
-** This code has been made independent of the rest of the time
-** conversion package to increase confidence in the verification it provides.
-** You can use this code to help in verifying other implementations.
-** To do this, compile with -DUSE_LTZ=0 and link without the tz library.
-*/
-
#ifndef NETBSD_INSPIRED
# define NETBSD_INSPIRED 1
#endif
-#ifndef USE_LTZ
-# define USE_LTZ 1
-#endif
#include "private.h"
#include
@@ -146,7 +136,7 @@ sumsize(size_t a, size_t b)
/* Return a pointer to a newly allocated buffer of size SIZE, exiting
on failure. SIZE should be nonzero. */
-static void *
+static void * ATTRIBUTE_MALLOC
xmalloc(size_t size)
{
void *p = malloc(size);
diff --git a/zic.8 b/zic.8
index b4eface..d105b24 100644
--- a/zic.8
+++ b/zic.8
@@ -165,14 +165,14 @@ abbreviation must be unambiguous in context.
A rule line has the form
.nf
.ti +.5i
-.ta \w'Rule\0\0'u +\w'NAME\0\0'u +\w'FROM\0\0'u +\w'1973\0\0'u +\w'TYPE\0\0'u +\w'Apr\0\0'u +\w'lastSun\0\0'u +\w'2:00\0\0'u +\w'SAVE\0\0'u
+.ta \w'Rule\0\0'u +\w'NAME\0\0'u +\w'FROM\0\0'u +\w'1973\0\0'u +\w'TYPE\0\0'u +\w'Apr\0\0'u +\w'lastSun\0\0'u +\w'2:00s\0\0'u +\w'1:00d\0\0'u
.sp
Rule NAME FROM TO TYPE IN ON AT SAVE LETTER/S
.sp
For example:
.ti +.5i
.sp
-Rule US 1967 1973 \*- Apr lastSun 2:00 1:00 D
+Rule US 1967 1973 \*- Apr lastSun 2:00s 1:00d D
.sp
.fi
The fields that make up a rule line are:
@@ -251,10 +251,11 @@ Recognized forms include:
.nf
.in +.5i
.sp
-.ta \w'01:28:13\0\0'u
+.ta \w'00:19:32.13\0\0'u
2 time in hours
2:00 time in hours and minutes
01:28:14 time in hours, minutes, and seconds
+00:19:32.13 time with fractional seconds
15:00 24-hour format time (for times after noon)
260:00 260 hours after 00:00
\*-2:30 2.5 hours before 00:00
@@ -264,6 +265,12 @@ Recognized forms include:
.sp
where hour 0 is midnight at the start of the day,
and hour 24 is midnight at the end of the day.
+Although
+.I zic
+rounds times to the nearest integer second
+(breaking ties to the even integer), the fractions may be useful
+to other applications requiring greater precision.
+The source format does not specify any maximum precision.
Any of these forms may be followed by the letter
.B w
if the given time is local
@@ -288,16 +295,24 @@ field would show the specified date and time of day.
.TP
.B SAVE
Gives the amount of time to be added to local standard time when the rule is in
-effect.
+effect, and whether the resulting time is standard or daylight saving.
This field has the same format as the
.B AT
field
-(although, of course, the
-suffixes are not used).
+except with a different set of suffix letters:
+.B s
+for standard time and
+.B d
+for daylight saving time.
+The suffix letter is typically omitted, and defaults to
+.B s
+if the offset is zero and to
+.B d
+otherwise.
Negative offsets are allowed; in Ireland, for example, daylight saving
time is observed in winter and has a negative offset relative to
Irish Standard Time.
-Only the sum of standard time and this amount matters; for example,
+The offset is merely added to standard time; for example,
.I zic
does not distinguish a 10:30 standard time plus an 0:30
.B SAVE
@@ -357,7 +372,9 @@ begin the field with a minus sign if time must be subtracted from UT.
.TP
.B RULES
The name of the rules that apply in the time zone or,
-alternately, an amount of time to add to local standard time.
+alternatively, a field in the same format as a rule-line SAVE column,
+giving of the amount of time to be added to local standard time
+effect, and whether the resulting time is standard or daylight saving.
If this field is
.B \*-
then standard time always applies in the time zone.
@@ -371,7 +388,7 @@ The pair of characters
is used to show where the
.q "variable part"
of the time zone abbreviation goes.
-Alternately, a format can use the pair of characters
+Alternatively, a format can use the pair of characters
.B %z
to stand for the UT offset in the form
.RI \(+- hh ,
@@ -384,7 +401,7 @@ using the shortest form that does not lose information, where
and
.I ss
are the hours, minutes, and seconds east (+) or west (\(mi) of UT.
-Alternately,
+Alternatively,
a slash (/)
separates standard and daylight abbreviations.
To conform to POSIX, a time zone abbreviation should contain only
@@ -440,7 +457,7 @@ field should appear as the
field in some zone line.
The
.B LINK-NAME
-field is used as an alternate name for that zone;
+field is used as an alternative name for that zone;
it has the same syntax as a zone line's
.B NAME
field.
diff --git a/zic.8.txt b/zic.8.txt
index 870d8eb..fc91cb2 100644
--- a/zic.8.txt
+++ b/zic.8.txt
@@ -111,11 +111,11 @@ DESCRIPTION
A rule line has the form
- Rule NAME FROM TO TYPE IN ON AT SAVE LETTER/S
+ Rule NAME FROM TO TYPE IN ON AT SAVE LETTER/S
For example:
- Rule US 1967 1973 - Apr lastSun 2:00 1:00 D
+ Rule US 1967 1973 - Apr lastSun 2:00s 1:00d D
The fields that make up a rule line are:
@@ -158,16 +158,21 @@ DESCRIPTION
AT Gives the time of day at which the rule takes effect.
Recognized forms include:
- 2 time in hours
- 2:00 time in hours and minutes
- 01:28:14 time in hours, minutes, and seconds
- 15:00 24-hour format time (for times after noon)
- 260:00 260 hours after 00:00
- -2:30 2.5 hours before 00:00
- - equivalent to 0
+ 2 time in hours
+ 2:00 time in hours and minutes
+ 01:28:14 time in hours, minutes, and seconds
+ 00:19:32.13 time with fractional seconds
+ 15:00 24-hour format time (for times after noon)
+ 260:00 260 hours after 00:00
+ -2:30 2.5 hours before 00:00
+ - equivalent to 0
where hour 0 is midnight at the start of the day, and hour 24
- is midnight at the end of the day. Any of these forms may be
+ is midnight at the end of the day. Although zic rounds times
+ to the nearest integer second (breaking ties to the even
+ integer), the fractions may be useful to other applications
+ requiring greater precision. The source format does not
+ specify any maximum precision. Any of these forms may be
followed by the letter w if the given time is local "wall
clock" time, s if the given time is local "standard" time, or u
(or g or z) if the given time is universal time; in the absence
@@ -177,14 +182,17 @@ DESCRIPTION
the specified date and time of day.
SAVE Gives the amount of time to be added to local standard time
- when the rule is in effect. This field has the same format as
- the AT field (although, of course, the suffixes are not used).
- Negative offsets are allowed; in Ireland, for example, daylight
- saving time is observed in winter and has a negative offset
- relative to Irish Standard Time. Only the sum of standard time
- and this amount matters; for example, zic does not distinguish
- a 10:30 standard time plus an 0:30 SAVE from a 10:00 standard
- time plus a 1:00 SAVE.
+ when the rule is in effect, and whether the resulting time is
+ standard or daylight saving. This field has the same format as
+ the AT field except with a different set of suffix letters: s
+ for standard time and d for daylight saving time. The suffix
+ letter is typically omitted, and defaults to s if the offset is
+ zero and to d otherwise. Negative offsets are allowed; in
+ Ireland, for example, daylight saving time is observed in
+ winter and has a negative offset relative to Irish Standard
+ Time. The offset is merely added to standard time; for
+ example, zic does not distinguish a 10:30 standard time plus an
+ 0:30 SAVE from a 10:00 standard time plus a 1:00 SAVE.
LETTER/S
Gives the "variable part" (for example, the "S" or "D" in "EST"
@@ -213,20 +221,22 @@ DESCRIPTION
subtracted from UT.
RULES The name of the rules that apply in the time zone or,
- alternately, an amount of time to add to local standard time. If
- this field is - then standard time always applies in the time
- zone. When an amount of time is given, only the sum of standard
- time and this amount matters.
+ alternatively, a field in the same format as a rule-line SAVE
+ column, giving of the amount of time to be added to local
+ standard time effect, and whether the resulting time is standard
+ or daylight saving. If this field is - then standard time always
+ applies in the time zone. When an amount of time is given, only
+ the sum of standard time and this amount matters.
FORMAT
The format for time zone abbreviations in this time zone. The
pair of characters %s is used to show where the "variable part"
- of the time zone abbreviation goes. Alternately, a format can
+ of the time zone abbreviation goes. Alternatively, a format can
use the pair of characters %z to stand for the UT offset in the
form +-hh, +-hhmm, or +-hhmmss, using the shortest form that does
not lose information, where hh, mm, and ss are the hours,
- minutes, and seconds east (+) or west (-) of UT. Alternately, a
- slash (/) separates standard and daylight abbreviations. To
+ minutes, and seconds east (+) or west (-) of UT. Alternatively,
+ a slash (/) separates standard and daylight abbreviations. To
conform to POSIX, a time zone abbreviation should contain only
alphanumeric ASCII characters, "+" and "-".
@@ -263,8 +273,8 @@ DESCRIPTION
Link Europe/Istanbul Asia/Istanbul
The TARGET field should appear as the NAME field in some zone line.
- The LINK-NAME field is used as an alternate name for that zone; it has
- the same syntax as a zone line's NAME field.
+ The LINK-NAME field is used as an alternative name for that zone; it
+ has the same syntax as a zone line's NAME field.
Except for continuation lines, lines may appear in any order in the
input. However, the behavior is unspecified if multiple zone or link
diff --git a/zic.c b/zic.c
index 304410f..31f1092 100644
--- a/zic.c
+++ b/zic.c
@@ -41,6 +41,10 @@ typedef int_fast64_t zic_t;
#else
#define MKDIR_UMASK 0755
#endif
+/* Port to native MS-Windows and to ancient UNIX. */
+#if !defined S_ISDIR && defined S_IFDIR && defined S_IFMT
+# define S_ISDIR(mode) (((mode) & S_IFMT) == S_IFDIR)
+#endif
#if HAVE_SYS_WAIT_H
#include /* for WIFEXITED and WEXITSTATUS */
@@ -85,7 +89,9 @@ struct rule {
/* or wall clock time if 0 */
bool r_todisgmt; /* above is GMT if 1 */
/* or local time if 0 */
- zic_t r_stdoff; /* offset from standard time */
+ bool r_isdst; /* is this daylight saving time? */
+ zic_t r_stdoff; /* offset from default time (which is
+ usually standard time) */
const char * r_abbrvar; /* variable part of abbreviation */
bool r_todo; /* a rule to do (used in outzone) */
@@ -106,10 +112,11 @@ struct zone {
const char * z_name;
zic_t z_gmtoff;
- const char * z_rule;
+ char * z_rule;
const char * z_format;
char z_format_specifier;
+ bool z_isdst;
zic_t z_stdoff;
struct rule * z_rules;
@@ -149,6 +156,7 @@ static void dolink(const char *, const char *, bool);
static char ** getfields(char * buf);
static zic_t gethms(const char * string, const char * errstring,
bool);
+static zic_t getstdoff(char *, bool *);
static void infile(const char * filename);
static void inleap(char ** fields, int nfields);
static void inlink(char ** fields, int nfields);
@@ -439,7 +447,7 @@ memcheck(void *ptr)
return ptr;
}
-static void *
+static void * ATTRIBUTE_MALLOC
emalloc(size_t size)
{
return memcheck(malloc(size));
@@ -451,7 +459,7 @@ erealloc(void *ptr, size_t size)
return memcheck(realloc(ptr, size));
}
-static char *
+static char * ATTRIBUTE_MALLOC
ecpyalloc (char const *str)
{
return memcheck(strdup(str));
@@ -893,9 +901,11 @@ dolink(char const *fromfield, char const *tofield, bool staysymlink)
char *linkalloc = absolute ? NULL : relname(fromfield, tofield);
char const *contents = absolute ? fromfield : linkalloc;
int symlink_errno = symlink(contents, tofield) == 0 ? 0 : errno;
- if (symlink_errno == ENOENT && !todirs_made) {
+ if (!todirs_made
+ && (symlink_errno == ENOENT || symlink_errno == ENOTSUP)) {
mkdirs(tofield, true);
- symlink_errno = symlink(contents, tofield) == 0 ? 0 : errno;
+ if (symlink_errno == ENOENT)
+ symlink_errno = symlink(contents, tofield) == 0 ? 0 : errno;
}
free(linkalloc);
if (symlink_errno == 0) {
@@ -1082,8 +1092,7 @@ associate(void)
** Maybe we have a local standard time offset.
*/
eat(zp->z_filename, zp->z_linenum);
- zp->z_stdoff = gethms(zp->z_rule, _("unruly zone"),
- true);
+ zp->z_stdoff = getstdoff(zp->z_rule, &zp->z_isdst);
/*
** Note, though, that if there's no rule,
** a '%s' in the format is a bad thing.
@@ -1190,8 +1199,10 @@ static zic_t
gethms(char const *string, char const *errstring, bool signable)
{
zic_t hh;
- int mm, ss, sign;
- char xs;
+ int sign, mm = 0, ss = 0;
+ char hhx, mmx, ssx, xr = '0', xs;
+ int tenths = 0;
+ bool ok = true;
if (string == NULL || *string == '\0')
return 0;
@@ -1201,12 +1212,24 @@ gethms(char const *string, char const *errstring, bool signable)
sign = -1;
++string;
} else sign = 1;
- if (sscanf(string, "%"SCNdZIC"%c", &hh, &xs) == 1)
- mm = ss = 0;
- else if (sscanf(string, "%"SCNdZIC":%d%c", &hh, &mm, &xs) == 2)
- ss = 0;
- else if (sscanf(string, "%"SCNdZIC":%d:%d%c", &hh, &mm, &ss, &xs)
- != 3) {
+ switch (sscanf(string,
+ "%"SCNdZIC"%c%d%c%d%c%1d%*[0]%c%*[0123456789]%c",
+ &hh, &hhx, &mm, &mmx, &ss, &ssx, &tenths, &xr, &xs)) {
+ default: ok = false; break;
+ case 8:
+ ok = '0' <= xr && xr <= '9';
+ /* fallthrough */
+ case 7:
+ ok &= ssx == '.';
+ if (ok && noise)
+ warning(_("fractional seconds rejected by"
+ " pre-2018 versions of zic"));
+ /* fallthrough */
+ case 5: ok &= mmx == ':'; /* fallthrough */
+ case 3: ok &= hhx == ':'; /* fallthrough */
+ case 1: break;
+ }
+ if (!ok) {
error("%s", errstring);
return 0;
}
@@ -1220,6 +1243,7 @@ gethms(char const *string, char const *errstring, bool signable)
error(_("time overflow"));
return 0;
}
+ ss += 5 + ((ss ^ 1) & (xr == '0')) <= tenths; /* Round to even. */
if (noise && (hh > HOURSPERDAY ||
(hh == HOURSPERDAY && (mm != 0 || ss != 0))))
warning(_("values over 24 hours not handled by pre-2007 versions of zic"));
@@ -1227,6 +1251,24 @@ warning(_("values over 24 hours not handled by pre-2007 versions of zic"));
sign * (mm * SECSPERMIN + ss));
}
+static zic_t
+getstdoff(char *field, bool *isdst)
+{
+ int dst = -1;
+ zic_t stdoff;
+ size_t fieldlen = strlen(field);
+ if (fieldlen != 0) {
+ char *ep = field + fieldlen - 1;
+ switch (*ep) {
+ case 'd': dst = 1; *ep = '\0'; break;
+ case 's': dst = 0; *ep = '\0'; break;
+ }
+ }
+ stdoff = gethms(field, _("invalid saved time"), true);
+ *isdst = dst < 0 ? stdoff != 0 : dst;
+ return stdoff;
+}
+
static void
inrule(char **fields, int nfields)
{
@@ -1242,7 +1284,7 @@ inrule(char **fields, int nfields)
}
r.r_filename = filename;
r.r_linenum = linenum;
- r.r_stdoff = gethms(fields[RF_STDOFF], _("invalid saved time"), true);
+ r.r_stdoff = getstdoff(fields[RF_STDOFF], &r.r_isdst);
rulesub(&r, fields[RF_LOYEAR], fields[RF_HIYEAR], fields[RF_COMMAND],
fields[RF_MONTH], fields[RF_DAY], fields[RF_TOD]);
r.r_name = ecpyalloc(fields[RF_NAME]);
@@ -2090,7 +2132,7 @@ abbroffset(char *buf, zic_t offset)
static size_t
doabbr(char *abbr, struct zone const *zp, char const *letters,
- zic_t stdoff, bool doquotes)
+ bool isdst, zic_t stdoff, bool doquotes)
{
register char * cp;
register char * slashp;
@@ -2105,7 +2147,7 @@ doabbr(char *abbr, struct zone const *zp, char const *letters,
else if (!letters)
letters = "%s";
sprintf(abbr, format, letters);
- } else if (stdoff != 0) {
+ } else if (isdst) {
strcpy(abbr, slashp + 1);
} else {
memcpy(abbr, format, slashp - format);
@@ -2216,7 +2258,7 @@ stringrule(char *result, const struct rule *const rp, const zic_t dstoff,
}
if (rp->r_todisgmt)
tod += gmtoff;
- if (rp->r_todisstd && rp->r_stdoff == 0)
+ if (rp->r_todisstd && !rp->r_isdst)
tod += dstoff;
if (tod != 2 * SECSPERMIN * MINSPERHOUR) {
*result++ = '/';
@@ -2273,7 +2315,7 @@ stringzone(char *result, struct zone const *zpfirst, ptrdiff_t zonecount)
continue;
if (rp->r_yrtype != NULL)
continue;
- if (rp->r_stdoff == 0) {
+ if (!rp->r_isdst) {
if (stdrp == NULL)
stdrp = rp;
else return -1;
@@ -2292,7 +2334,7 @@ stringzone(char *result, struct zone const *zpfirst, ptrdiff_t zonecount)
register struct rule *stdabbrrp = NULL;
for (i = 0; i < zp->z_nrules; ++i) {
rp = &zp->z_rules[i];
- if (rp->r_stdoff == 0 && rule_cmp(stdabbrrp, rp) < 0)
+ if (!rp->r_isdst && rule_cmp(stdabbrrp, rp) < 0)
stdabbrrp = rp;
if (rule_cmp(stdrp, rp) < 0)
stdrp = rp;
@@ -2305,13 +2347,14 @@ stringzone(char *result, struct zone const *zpfirst, ptrdiff_t zonecount)
if (stdrp != NULL && stdrp->r_hiyear == 2037)
return YEAR_BY_YEAR_ZONE;
- if (stdrp != NULL && stdrp->r_stdoff != 0) {
+ if (stdrp != NULL && stdrp->r_isdst) {
/* Perpetual DST. */
dstr.r_month = TM_JANUARY;
dstr.r_dycode = DC_DOM;
dstr.r_dayofmonth = 1;
dstr.r_tod = 0;
dstr.r_todisstd = dstr.r_todisgmt = false;
+ dstr.r_isdst = stdrp->r_isdst;
dstr.r_stdoff = stdrp->r_stdoff;
dstr.r_abbrvar = stdrp->r_abbrvar;
stdr.r_month = TM_DECEMBER;
@@ -2319,6 +2362,7 @@ stringzone(char *result, struct zone const *zpfirst, ptrdiff_t zonecount)
stdr.r_dayofmonth = 31;
stdr.r_tod = SECSPERDAY + stdrp->r_stdoff;
stdr.r_todisstd = stdr.r_todisgmt = false;
+ stdr.r_isdst = false;
stdr.r_stdoff = 0;
stdr.r_abbrvar
= (stdabbrrp ? stdabbrrp->r_abbrvar : "");
@@ -2326,10 +2370,10 @@ stringzone(char *result, struct zone const *zpfirst, ptrdiff_t zonecount)
stdrp = &stdr;
}
}
- if (stdrp == NULL && (zp->z_nrules != 0 || zp->z_stdoff != 0))
+ if (stdrp == NULL && (zp->z_nrules != 0 || zp->z_isdst))
return -1;
abbrvar = (stdrp == NULL) ? "" : stdrp->r_abbrvar;
- len = doabbr(result, zp, abbrvar, 0, true);
+ len = doabbr(result, zp, abbrvar, false, 0, true);
offsetlen = stringoffset(result + len, -zp->z_gmtoff);
if (! offsetlen) {
result[0] = '\0';
@@ -2338,7 +2382,8 @@ stringzone(char *result, struct zone const *zpfirst, ptrdiff_t zonecount)
len += offsetlen;
if (dstrp == NULL)
return compat;
- len += doabbr(result + len, zp, dstrp->r_abbrvar, dstrp->r_stdoff, true);
+ len += doabbr(result + len, zp, dstrp->r_abbrvar,
+ dstrp->r_isdst, dstrp->r_stdoff, true);
if (dstrp->r_stdoff != SECSPERMIN * MINSPERHOUR) {
offsetlen = stringoffset(result + len,
-(zp->z_gmtoff + dstrp->r_stdoff));
@@ -2514,9 +2559,9 @@ outzone(const struct zone *zpfirst, ptrdiff_t zonecount)
startoff = zp->z_gmtoff;
if (zp->z_nrules == 0) {
stdoff = zp->z_stdoff;
- doabbr(startbuf, zp, NULL, stdoff, false);
+ doabbr(startbuf, zp, NULL, zp->z_isdst, stdoff, false);
type = addtype(oadd(zp->z_gmtoff, stdoff),
- startbuf, stdoff != 0, startttisstd,
+ startbuf, zp->z_isdst, startttisstd,
startttisgmt);
if (usestart) {
addtt(starttime, type);
@@ -2612,6 +2657,7 @@ outzone(const struct zone *zpfirst, ptrdiff_t zonecount)
stdoff);
doabbr(startbuf, zp,
rp->r_abbrvar,
+ rp->r_isdst,
rp->r_stdoff,
false);
continue;
@@ -2622,6 +2668,7 @@ outzone(const struct zone *zpfirst, ptrdiff_t zonecount)
doabbr(startbuf,
zp,
rp->r_abbrvar,
+ rp->r_isdst,
rp->r_stdoff,
false);
}
@@ -2629,9 +2676,9 @@ outzone(const struct zone *zpfirst, ptrdiff_t zonecount)
eats(zp->z_filename, zp->z_linenum,
rp->r_filename, rp->r_linenum);
doabbr(ab, zp, rp->r_abbrvar,
- rp->r_stdoff, false);
+ rp->r_isdst, rp->r_stdoff, false);
offset = oadd(zp->z_gmtoff, rp->r_stdoff);
- type = addtype(offset, ab, rp->r_stdoff != 0,
+ type = addtype(offset, ab, rp->r_isdst,
rp->r_todisstd, rp->r_todisgmt);
if (rp->r_hiyear == ZIC_MAX
&& ! (0 <= lastatmax
diff --git a/ziguard.awk b/ziguard.awk
new file mode 100644
index 0000000..42e2910
--- /dev/null
+++ b/ziguard.awk
@@ -0,0 +1,100 @@
+# Convert tzdata source into vanguard or rearguard form.
+
+# Contributed by Paul Eggert. This file is in the public domain.
+
+# This is not a general-purpose converter; it is designed for current tzdata.
+#
+# When converting to vanguard form, the output can use negative SAVE
+# values.
+#
+# When converting to rearguard form, the output uses only nonnegative
+# SAVE values. The idea is for the output data to simulate the behavior
+# of the input data as best it can within the constraints of the
+# rearguard format.
+
+BEGIN {
+ dataform_type["vanguard"] = 1
+ dataform_type["main"] = 1
+ dataform_type["rearguard"] = 1
+
+ # The command line should set DATAFORM.
+ if (!dataform_type[DATAFORM]) exit 1
+ vanguard = DATAFORM == "vanguard"
+}
+
+/^Zone/ { zone = $2 }
+
+DATAFORM != "main" {
+ in_comment = /^#/
+ uncomment = comment_out = 0
+
+ # If the line should differ due to Czechoslovakia using negative SAVE values,
+ # uncomment the desired version and comment out the undesired one.
+ if (zone == "Europe/Prague" && /1947 Feb 23/) {
+ if (($(in_comment + 2) != "-") == vanguard) {
+ uncomment = in_comment
+ } else {
+ comment_out = !in_comment
+ }
+ }
+
+ # If this line should differ due to Ireland using negative SAVE values,
+ # uncomment the desired version and comment out the undesired one.
+ Rule_Eire = /^#?Rule[\t ]+Eire[\t ]/
+ Zone_Dublin_post_1968 \
+ = (zone == "Europe/Dublin" && /^#?[\t ]+[01]:00[\t ]/ \
+ && (!$(in_comment + 4) || 1968 < $(in_comment + 4)))
+ if (Rule_Eire || Zone_Dublin_post_1968) {
+ if ((Rule_Eire \
+ || (Zone_Dublin_post_1968 && $(in_comment + 3) == "IST/GMT")) \
+ == vanguard) {
+ uncomment = in_comment
+ } else {
+ comment_out = !in_comment
+ }
+ }
+
+ # If this line should differ due to Namibia using Rule SAVE suffixes,
+ # uncomment the desired version and comment out the undesired one.
+ Rule_Namibia = /^#?Rule[\t ]+Namibia[\t ]/
+ Zone_using_Namibia_rule \
+ = (zone == "Africa/Windhoek" \
+ && ($(in_comment + 2) == "Namibia" \
+ || (1994 <= $(in_comment + 4) && $(in_comment + 4) <= 2017) \
+ || in_comment + 3 == NF))
+ if (Rule_Namibia || Zone_using_Namibia_rule) {
+ if ((Rule_Namibia \
+ ? ($(in_comment + 9) ~ /^-/ \
+ || ($(in_comment + 9) == 0 && $(in_comment + 10) == "CAT")) \
+ : $(in_comment + 1) == "2:00" && $(in_comment + 2) == "Namibia") \
+ == vanguard) {
+ uncomment = in_comment
+ } else {
+ comment_out = !in_comment
+ }
+ }
+
+ if (uncomment) {
+ sub(/^#/, "")
+ }
+ if (comment_out) {
+ sub(/^/, "#")
+ }
+}
+
+# If a Link line is followed by a Zone line for the same data, comment
+# out the Link line. This can happen if backzone overrides a Link
+# with a Zone.
+/^Link/ {
+ linkline[$3] = NR
+}
+/^Zone/ {
+ sub(/^Link/, "#Link", line[linkline[$2]])
+}
+
+{ line[NR] = $0 }
+
+END {
+ for (i = 1; i <= NR; i++)
+ print line[i]
+}
diff --git a/zishrink.awk b/zishrink.awk
index 23d623e..d617644 100644
--- a/zishrink.awk
+++ b/zishrink.awk
@@ -37,7 +37,7 @@ function process_input_line(line, field, end, i, n, startdef)
# Remove comments, normalize spaces, and append a space to each line.
sub(/#.*/, "", line)
line = line " "
- gsub(/[\f\r\t\v ]+/, " ", line)
+ gsub(/[\t ]+/, " ", line)
# Abbreviate keywords. Do not abbreviate "Link" to just "L",
# as pre-2017c zic erroneously diagnoses "Li" as ambiguous.
@@ -148,7 +148,7 @@ BEGIN {
print "# This zic input file is in the public domain."
}
-/^[\f\r\t\v ]*[^#\f\r\t\v ]/ {
+/^[\t ]*[^#\t ]/ {
process_input_line($0)
}
diff --git a/zone.tab b/zone.tab
index e1bfdee..f92c919 100644
--- a/zone.tab
+++ b/zone.tab
@@ -429,7 +429,7 @@ US +593249-1394338 America/Yakutat Alaska - Yakutat
US +643004-1652423 America/Nome Alaska (west)
US +515248-1763929 America/Adak Aleutian Islands
US +211825-1575130 Pacific/Honolulu Hawaii
-UY -3453-05611 America/Montevideo
+UY -345433-0561245 America/Montevideo
UZ +3940+06648 Asia/Samarkand Uzbekistan (west)
UZ +4120+06918 Asia/Tashkent Uzbekistan (east)
VA +415408+0122711 Europe/Vatican
diff --git a/zone1970.tab b/zone1970.tab
index 4ee8ce5..2d90ed7 100644
--- a/zone1970.tab
+++ b/zone1970.tab
@@ -12,7 +12,7 @@
# of ISO 3166 2-character country codes. See the file 'iso3166.tab'.
# 2. Latitude and longitude of the zone's principal location
# in ISO 6709 sign-degrees-minutes-seconds format,
-# either +-DDMM+-DDDMM or +-DDMMSS+-DDDMMSS,
+# either ±DDMM±DDDMM or ±DDMMSS±DDDMMSS,
# first latitude (+ is north), then longitude (+ is east).
# 3. Zone name used in value of TZ environment variable.
# Please see the theory.html file for how zone names are chosen.
@@ -371,7 +371,7 @@ US +593249-1394338 America/Yakutat Alaska - Yakutat
US +643004-1652423 America/Nome Alaska (west)
US +515248-1763929 America/Adak Aleutian Islands
US,UM +211825-1575130 Pacific/Honolulu Hawaii
-UY -3453-05611 America/Montevideo
+UY -345433-0561245 America/Montevideo
UZ +3940+06648 Asia/Samarkand Uzbekistan (west)
UZ +4120+06918 Asia/Tashkent Uzbekistan (east)
VE +1030-06656 America/Caracas
diff --git a/zoneinfo2tdf.pl b/zoneinfo2tdf.pl
old mode 100755
new mode 100644
--
2.7.4