1 // Licensed to the .NET Foundation under one or more agreements.
2 // The .NET Foundation licenses this file to you under the MIT license.
3 // See the LICENSE file in the project root for more information.
5 using System.Collections.Generic;
6 using System.Diagnostics;
7 using System.Globalization;
10 using System.Threading;
11 using System.Security;
17 public sealed partial class TimeZoneInfo
19 private const string DefaultTimeZoneDirectory = "/usr/share/zoneinfo/";
20 private const string ZoneTabFileName = "zone.tab";
21 private const string TimeZoneEnvironmentVariable = "TZ";
22 private const string TimeZoneDirectoryEnvironmentVariable = "TZDIR";
24 private TimeZoneInfo(byte[] data, string id, bool dstDisabled)
28 byte[] typeOfLocalTime;
29 TZifType[] transitionType;
30 string zoneAbbreviations;
33 string futureTransitionsPosixFormat;
35 // parse the raw TZif bytes; this method can throw ArgumentException when the data is malformed.
36 TZif_ParseRaw(data, out t, out dts, out typeOfLocalTime, out transitionType, out zoneAbbreviations, out StandardTime, out GmtTime, out futureTransitionsPosixFormat);
39 _displayName = LocalId;
40 _baseUtcOffset = TimeSpan.Zero;
42 // find the best matching baseUtcOffset and display strings based on the current utcNow value.
43 // NOTE: read the display strings from the tzfile now in case they can't be loaded later
44 // from the globalization data.
45 DateTime utcNow = DateTime.UtcNow;
46 for (int i = 0; i < dts.Length && dts[i] <= utcNow; i++)
48 int type = typeOfLocalTime[i];
49 if (!transitionType[type].IsDst)
51 _baseUtcOffset = transitionType[type].UtcOffset;
52 _standardDisplayName = TZif_GetZoneAbbreviation(zoneAbbreviations, transitionType[type].AbbreviationIndex);
56 _daylightDisplayName = TZif_GetZoneAbbreviation(zoneAbbreviations, transitionType[type].AbbreviationIndex);
62 // time zones like Africa/Bujumbura and Etc/GMT* have no transition times but still contain
63 // TZifType entries that may contain a baseUtcOffset and display strings
64 for (int i = 0; i < transitionType.Length; i++)
66 if (!transitionType[i].IsDst)
68 _baseUtcOffset = transitionType[i].UtcOffset;
69 _standardDisplayName = TZif_GetZoneAbbreviation(zoneAbbreviations, transitionType[i].AbbreviationIndex);
73 _daylightDisplayName = TZif_GetZoneAbbreviation(zoneAbbreviations, transitionType[i].AbbreviationIndex);
77 _displayName = _standardDisplayName;
79 GetDisplayName(Interop.Globalization.TimeZoneDisplayNameType.Generic, ref _displayName);
80 GetDisplayName(Interop.Globalization.TimeZoneDisplayNameType.Standard, ref _standardDisplayName);
81 GetDisplayName(Interop.Globalization.TimeZoneDisplayNameType.DaylightSavings, ref _daylightDisplayName);
83 // TZif supports seconds-level granularity with offsets but TimeZoneInfo only supports minutes since it aligns
84 // with DateTimeOffset, SQL Server, and the W3C XML Specification
85 if (_baseUtcOffset.Ticks % TimeSpan.TicksPerMinute != 0)
87 _baseUtcOffset = new TimeSpan(_baseUtcOffset.Hours, _baseUtcOffset.Minutes, 0);
92 // only create the adjustment rule if DST is enabled
93 TZif_GenerateAdjustmentRules(out _adjustmentRules, _baseUtcOffset, dts, typeOfLocalTime, transitionType, StandardTime, GmtTime, futureTransitionsPosixFormat);
96 ValidateTimeZoneInfo(_id, _baseUtcOffset, _adjustmentRules, out _supportsDaylightSavingTime);
99 private void GetDisplayName(Interop.Globalization.TimeZoneDisplayNameType nameType, ref string displayName)
101 if (GlobalizationMode.Invariant)
103 displayName = _standardDisplayName;
107 string timeZoneDisplayName;
108 bool result = Interop.CallStringMethod(
109 (locale, id, type, stringBuilder) => Interop.Globalization.GetTimeZoneDisplayName(
114 stringBuilder.Capacity),
115 CultureInfo.CurrentUICulture.Name,
118 out timeZoneDisplayName);
120 // If there is an unknown error, don't set the displayName field.
121 // It will be set to the abbreviation that was read out of the tzfile.
124 displayName = timeZoneDisplayName;
129 /// Returns a cloned array of AdjustmentRule objects
131 public AdjustmentRule[] GetAdjustmentRules()
133 if (_adjustmentRules == null)
135 return Array.Empty<AdjustmentRule>();
138 // The rules we use in Unix care mostly about the start and end dates but don't fill the transition start and end info.
139 // as the rules now is public, we should fill it properly so the caller doesn't have to know how we use it internally
140 // and can use it as it is used in Windows
142 AdjustmentRule[] rules = new AdjustmentRule[_adjustmentRules.Length];
144 for (int i = 0; i < _adjustmentRules.Length; i++)
146 var rule = _adjustmentRules[i];
147 var start = rule.DateStart.Kind == DateTimeKind.Utc ?
148 // At the daylight start we didn't start the daylight saving yet then we convert to Local time
149 // by adding the _baseUtcOffset to the UTC time
150 new DateTime(rule.DateStart.Ticks + _baseUtcOffset.Ticks, DateTimeKind.Unspecified) :
152 var end = rule.DateEnd.Kind == DateTimeKind.Utc ?
153 // At the daylight saving end, the UTC time is mapped to local time which is already shifted by the daylight delta
154 // we calculate the local time by adding _baseUtcOffset + DaylightDelta to the UTC time
155 new DateTime(rule.DateEnd.Ticks + _baseUtcOffset.Ticks + rule.DaylightDelta.Ticks, DateTimeKind.Unspecified) :
158 var startTransition = TimeZoneInfo.TransitionTime.CreateFixedDateRule(new DateTime(1, 1, 1, start.Hour, start.Minute, start.Second), start.Month, start.Day);
159 var endTransition = TimeZoneInfo.TransitionTime.CreateFixedDateRule(new DateTime(1, 1, 1, end.Hour, end.Minute, end.Second), end.Month, end.Day);
161 rules[i] = TimeZoneInfo.AdjustmentRule.CreateAdjustmentRule(start.Date, end.Date, rule.DaylightDelta, startTransition, endTransition);
167 private static void PopulateAllSystemTimeZones(CachedData cachedData)
169 Debug.Assert(Monitor.IsEntered(cachedData));
171 string timeZoneDirectory = GetTimeZoneDirectory();
172 foreach (string timeZoneId in GetTimeZoneIds(timeZoneDirectory))
176 TryGetTimeZone(timeZoneId, false, out value, out ex, cachedData, alwaysFallbackToLocalMachine: true); // populate the cache
181 /// Helper function for retrieving the local system time zone.
182 /// May throw COMException, TimeZoneNotFoundException, InvalidTimeZoneException.
183 /// Assumes cachedData lock is taken.
185 /// <returns>A new TimeZoneInfo instance.</returns>
186 private static TimeZoneInfo GetLocalTimeZone(CachedData cachedData)
188 Debug.Assert(Monitor.IsEntered(cachedData));
190 // Without Registry support, create the TimeZoneInfo from a TZ file
191 return GetLocalTimeZoneFromTzFile();
194 private static TimeZoneInfoResult TryGetTimeZoneFromLocalMachine(string id, out TimeZoneInfo value, out Exception e)
199 string timeZoneDirectory = GetTimeZoneDirectory();
200 string timeZoneFilePath = Path.Combine(timeZoneDirectory, id);
204 rawData = File.ReadAllBytes(timeZoneFilePath);
206 catch (UnauthorizedAccessException ex)
209 return TimeZoneInfoResult.SecurityException;
211 catch (FileNotFoundException ex)
214 return TimeZoneInfoResult.TimeZoneNotFoundException;
216 catch (DirectoryNotFoundException ex)
219 return TimeZoneInfoResult.TimeZoneNotFoundException;
221 catch (IOException ex)
223 e = new InvalidTimeZoneException(SR.Format(SR.InvalidTimeZone_InvalidFileData, id, timeZoneFilePath), ex);
224 return TimeZoneInfoResult.InvalidTimeZoneException;
227 value = GetTimeZoneFromTzData(rawData, id);
231 e = new InvalidTimeZoneException(SR.Format(SR.InvalidTimeZone_InvalidFileData, id, timeZoneFilePath));
232 return TimeZoneInfoResult.InvalidTimeZoneException;
235 return TimeZoneInfoResult.Success;
239 /// Returns a collection of TimeZone Id values from the zone.tab file in the timeZoneDirectory.
242 /// Lines that start with # are comments and are skipped.
244 private static List<string> GetTimeZoneIds(string timeZoneDirectory)
246 List<string> timeZoneIds = new List<string>();
250 using (StreamReader sr = new StreamReader(Path.Combine(timeZoneDirectory, ZoneTabFileName), Encoding.UTF8))
252 string zoneTabFileLine;
253 while ((zoneTabFileLine = sr.ReadLine()) != null)
255 if (!string.IsNullOrEmpty(zoneTabFileLine) && zoneTabFileLine[0] != '#')
257 // the format of the line is "country-code \t coordinates \t TimeZone Id \t comments"
259 int firstTabIndex = zoneTabFileLine.IndexOf('\t');
260 if (firstTabIndex != -1)
262 int secondTabIndex = zoneTabFileLine.IndexOf('\t', firstTabIndex + 1);
263 if (secondTabIndex != -1)
266 int startIndex = secondTabIndex + 1;
267 int thirdTabIndex = zoneTabFileLine.IndexOf('\t', startIndex);
268 if (thirdTabIndex != -1)
270 int length = thirdTabIndex - startIndex;
271 timeZoneId = zoneTabFileLine.Substring(startIndex, length);
275 timeZoneId = zoneTabFileLine.Substring(startIndex);
278 if (!string.IsNullOrEmpty(timeZoneId))
280 timeZoneIds.Add(timeZoneId);
288 catch (IOException) { }
289 catch (UnauthorizedAccessException) { }
295 /// Gets the tzfile raw data for the current 'local' time zone using the following rules.
296 /// 1. Read the TZ environment variable. If it is set, use it.
297 /// 2. Look for the data in /etc/localtime.
298 /// 3. Look for the data in GetTimeZoneDirectory()/localtime.
299 /// 4. Use UTC if all else fails.
301 private static bool TryGetLocalTzFile(out byte[] rawData, out string id)
305 string tzVariable = GetTzEnvironmentVariable();
307 // If the env var is null, use the localtime file
308 if (tzVariable == null)
311 TryLoadTzFile("/etc/localtime", ref rawData, ref id) ||
312 TryLoadTzFile(Path.Combine(GetTimeZoneDirectory(), "localtime"), ref rawData, ref id);
315 // If it's empty, use UTC (TryGetLocalTzFile() should return false).
316 if (tzVariable.Length == 0)
321 // Otherwise, use the path from the env var. If it's not absolute, make it relative
322 // to the system timezone directory
324 if (tzVariable[0] != '/')
327 tzFilePath = Path.Combine(GetTimeZoneDirectory(), tzVariable);
331 tzFilePath = tzVariable;
333 return TryLoadTzFile(tzFilePath, ref rawData, ref id);
336 private static string GetTzEnvironmentVariable()
338 string result = Environment.GetEnvironmentVariable(TimeZoneEnvironmentVariable);
339 if (!string.IsNullOrEmpty(result))
341 if (result[0] == ':')
343 // strip off the ':' prefix
344 result = result.Substring(1);
351 private static bool TryLoadTzFile(string tzFilePath, ref byte[] rawData, ref string id)
353 if (File.Exists(tzFilePath))
357 rawData = File.ReadAllBytes(tzFilePath);
358 if (string.IsNullOrEmpty(id))
360 id = FindTimeZoneIdUsingReadLink(tzFilePath);
362 if (string.IsNullOrEmpty(id))
364 id = FindTimeZoneId(rawData);
369 catch (IOException) { }
370 catch (SecurityException) { }
371 catch (UnauthorizedAccessException) { }
377 /// Finds the time zone id by using 'readlink' on the path to see if tzFilePath is
378 /// a symlink to a file.
380 private static string FindTimeZoneIdUsingReadLink(string tzFilePath)
384 string symlinkPath = Interop.Sys.ReadLink(tzFilePath);
385 if (symlinkPath != null)
387 // Use Path.Combine to resolve links that contain a relative path (e.g. /etc/localtime).
388 symlinkPath = Path.Combine(tzFilePath, symlinkPath);
390 string timeZoneDirectory = GetTimeZoneDirectory();
391 if (symlinkPath.StartsWith(timeZoneDirectory, StringComparison.Ordinal))
393 id = symlinkPath.Substring(timeZoneDirectory.Length);
403 private static IEnumerable<string> EnumerateFilesRecursively(string path)
405 List<string> toExplore = null; // List used as a stack
407 string currentPath = path;
410 using (Microsoft.Win32.SafeHandles.SafeDirectoryHandle dirHandle = Interop.Sys.OpenDir(currentPath))
412 if (dirHandle.IsInvalid)
414 throw Interop.GetExceptionForIoErrno(Interop.Sys.GetLastErrorInfo(), currentPath, isDirectory: true);
417 // Read each entry from the enumerator
418 Interop.Sys.DirectoryEntry dirent;
419 while (Interop.Sys.ReadDir(dirHandle, out dirent) == 0)
421 if (dirent.InodeName == "." || dirent.InodeName == "..")
424 string fullPath = Path.Combine(currentPath, dirent.InodeName);
426 // Get from the dir entry whether the entry is a file or directory.
427 // We classify everything as a file unless we know it to be a directory.
429 if (dirent.InodeType == Interop.Sys.NodeType.DT_DIR)
431 // We know it's a directory.
434 else if (dirent.InodeType == Interop.Sys.NodeType.DT_LNK || dirent.InodeType == Interop.Sys.NodeType.DT_UNKNOWN)
436 // It's a symlink or unknown: stat to it to see if we can resolve it to a directory.
437 // If we can't (e.g. symlink to a file, broken symlink, etc.), we'll just treat it as a file.
439 Interop.Sys.FileStatus fileinfo;
440 if (Interop.Sys.Stat(fullPath, out fileinfo) >= 0)
442 isDir = (fileinfo.Mode & Interop.Sys.FileTypes.S_IFMT) == Interop.Sys.FileTypes.S_IFDIR;
451 // Otherwise, treat it as a file. This includes regular files, FIFOs, etc.
455 // Yield the result if the user has asked for it. In the case of directories,
456 // always explore it by pushing it onto the stack, regardless of whether
457 // we're returning directories.
460 if (toExplore == null)
462 toExplore = new List<string>();
464 toExplore.Add(fullPath);
468 yield return fullPath;
473 if (toExplore == null || toExplore.Count == 0)
476 currentPath = toExplore[toExplore.Count - 1];
477 toExplore.RemoveAt(toExplore.Count - 1);
482 /// Find the time zone id by searching all the tzfiles for the one that matches rawData
483 /// and return its file name.
485 private static string FindTimeZoneId(byte[] rawData)
487 // default to "Local" if we can't find the right tzfile
489 string timeZoneDirectory = GetTimeZoneDirectory();
490 string localtimeFilePath = Path.Combine(timeZoneDirectory, "localtime");
491 string posixrulesFilePath = Path.Combine(timeZoneDirectory, "posixrules");
492 byte[] buffer = new byte[rawData.Length];
496 foreach (string filePath in EnumerateFilesRecursively(timeZoneDirectory))
498 // skip the localtime and posixrules file, since they won't give us the correct id
499 if (!string.Equals(filePath, localtimeFilePath, StringComparison.OrdinalIgnoreCase)
500 && !string.Equals(filePath, posixrulesFilePath, StringComparison.OrdinalIgnoreCase))
502 if (CompareTimeZoneFile(filePath, buffer, rawData))
504 // if all bytes are the same, this must be the right tz file
507 // strip off the root time zone directory
508 if (id.StartsWith(timeZoneDirectory, StringComparison.Ordinal))
510 id = id.Substring(timeZoneDirectory.Length);
517 catch (IOException) { }
518 catch (SecurityException) { }
519 catch (UnauthorizedAccessException) { }
524 private static bool CompareTimeZoneFile(string filePath, byte[] buffer, byte[] rawData)
528 // bufferSize == 1 used to avoid unnecessary buffer in FileStream
529 using (FileStream stream = new FileStream(filePath, FileMode.Open, FileAccess.Read, FileShare.Read, bufferSize: 1))
531 if (stream.Length == rawData.Length)
534 int count = rawData.Length;
538 int n = stream.Read(buffer, index, count);
540 throw Error.GetEndOfFile();
543 for (; index < end; index++)
545 if (buffer[index] != rawData[index])
558 catch (IOException) { }
559 catch (SecurityException) { }
560 catch (UnauthorizedAccessException) { }
566 /// Helper function used by 'GetLocalTimeZone()' - this function wraps the call
567 /// for loading time zone data from computers without Registry support.
569 /// The TryGetLocalTzFile() call returns a Byte[] containing the compiled tzfile.
571 private static TimeZoneInfo GetLocalTimeZoneFromTzFile()
575 if (TryGetLocalTzFile(out rawData, out id))
577 TimeZoneInfo result = GetTimeZoneFromTzData(rawData, id);
584 // if we can't find a local time zone, return UTC
588 private static TimeZoneInfo GetTimeZoneFromTzData(byte[] rawData, string id)
594 return new TimeZoneInfo(rawData, id, dstDisabled: false); // create a TimeZoneInfo instance from the TZif data w/ DST support
596 catch (ArgumentException) { }
597 catch (InvalidTimeZoneException) { }
600 return new TimeZoneInfo(rawData, id, dstDisabled: true); // create a TimeZoneInfo instance from the TZif data w/o DST support
602 catch (ArgumentException) { }
603 catch (InvalidTimeZoneException) { }
609 private static string GetTimeZoneDirectory()
611 string tzDirectory = Environment.GetEnvironmentVariable(TimeZoneDirectoryEnvironmentVariable);
613 if (tzDirectory == null)
615 tzDirectory = DefaultTimeZoneDirectory;
617 else if (!tzDirectory.EndsWith(Path.DirectorySeparatorChar))
619 tzDirectory += Path.DirectorySeparatorChar;
626 /// Helper function for retrieving a TimeZoneInfo object by <time_zone_name>.
627 /// This function wraps the logic necessary to keep the private
628 /// SystemTimeZones cache in working order
630 /// This function will either return a valid TimeZoneInfo instance or
631 /// it will throw 'InvalidTimeZoneException' / 'TimeZoneNotFoundException'.
633 public static TimeZoneInfo FindSystemTimeZoneById(string id)
635 // Special case for Utc as it will not exist in the dictionary with the rest
636 // of the system time zones. There is no need to do this check for Local.Id
637 // since Local is a real time zone that exists in the dictionary cache
638 if (string.Equals(id, UtcId, StringComparison.OrdinalIgnoreCase))
645 throw new ArgumentNullException(nameof(id));
647 else if (id.Length == 0 || id.Contains('\0'))
649 throw new TimeZoneNotFoundException(SR.Format(SR.TimeZoneNotFound_MissingData, id));
655 TimeZoneInfoResult result;
657 CachedData cachedData = s_cachedData;
661 result = TryGetTimeZone(id, false, out value, out e, cachedData, alwaysFallbackToLocalMachine: true);
664 if (result == TimeZoneInfoResult.Success)
668 else if (result == TimeZoneInfoResult.InvalidTimeZoneException)
670 Debug.Assert(e is InvalidTimeZoneException,
671 "TryGetTimeZone must create an InvalidTimeZoneException when it returns TimeZoneInfoResult.InvalidTimeZoneException");
674 else if (result == TimeZoneInfoResult.SecurityException)
676 throw new SecurityException(SR.Format(SR.Security_CannotReadFileData, id), e);
680 throw new TimeZoneNotFoundException(SR.Format(SR.TimeZoneNotFound_MissingData, id), e);
684 // DateTime.Now fast path that avoids allocating an historically accurate TimeZoneInfo.Local and just creates a 1-year (current year) accurate time zone
685 internal static TimeSpan GetDateTimeNowUtcOffsetFromUtc(DateTime time, out bool isAmbiguousLocalDst)
687 bool isDaylightSavings;
688 // Use the standard code path for Unix since there isn't a faster way of handling current-year-only time zones
689 return GetUtcOffsetFromUtc(time, Local, out isDaylightSavings, out isAmbiguousLocalDst);
692 // TZFILE(5) BSD File Formats Manual TZFILE(5)
695 // tzfile -- timezone information
698 // #include "/usr/src/lib/libc/stdtime/tzfile.h"
701 // The time zone information files used by tzset(3) begin with the magic
702 // characters ``TZif'' to identify them as time zone information files, fol-
703 // lowed by sixteen bytes reserved for future use, followed by four four-
704 // byte values written in a ``standard'' byte order (the high-order byte of
705 // the value is written first). These values are, in order:
707 // tzh_ttisgmtcnt The number of UTC/local indicators stored in the file.
708 // tzh_ttisstdcnt The number of standard/wall indicators stored in the
710 // tzh_leapcnt The number of leap seconds for which data is stored in
712 // tzh_timecnt The number of ``transition times'' for which data is
713 // stored in the file.
714 // tzh_typecnt The number of ``local time types'' for which data is
715 // stored in the file (must not be zero).
716 // tzh_charcnt The number of characters of ``time zone abbreviation
717 // strings'' stored in the file.
719 // The above header is followed by tzh_timecnt four-byte values of type
720 // long, sorted in ascending order. These values are written in ``stan-
721 // dard'' byte order. Each is used as a transition time (as returned by
722 // time(3)) at which the rules for computing local time change. Next come
723 // tzh_timecnt one-byte values of type unsigned char; each one tells which
724 // of the different types of ``local time'' types described in the file is
725 // associated with the same-indexed transition time. These values serve as
726 // indices into an array of ttinfo structures that appears next in the file;
727 // these structures are defined as follows:
732 // unsigned int tt_abbrind;
735 // Each structure is written as a four-byte value for tt_gmtoff of type
736 // long, in a standard byte order, followed by a one-byte value for tt_isdst
737 // and a one-byte value for tt_abbrind. In each structure, tt_gmtoff gives
738 // the number of seconds to be added to UTC, tt_isdst tells whether tm_isdst
739 // should be set by localtime(3) and tt_abbrind serves as an index into the
740 // array of time zone abbreviation characters that follow the ttinfo struc-
741 // ture(s) in the file.
743 // Then there are tzh_leapcnt pairs of four-byte values, written in standard
744 // byte order; the first value of each pair gives the time (as returned by
745 // time(3)) at which a leap second occurs; the second gives the total number
746 // of leap seconds to be applied after the given time. The pairs of values
747 // are sorted in ascending order by time.b
749 // Then there are tzh_ttisstdcnt standard/wall indicators, each stored as a
750 // one-byte value; they tell whether the transition times associated with
751 // local time types were specified as standard time or wall clock time, and
752 // are used when a time zone file is used in handling POSIX-style time zone
753 // environment variables.
755 // Finally there are tzh_ttisgmtcnt UTC/local indicators, each stored as a
756 // one-byte value; they tell whether the transition times associated with
757 // local time types were specified as UTC or local time, and are used when a
758 // time zone file is used in handling POSIX-style time zone environment
761 // localtime uses the first standard-time ttinfo structure in the file (or
762 // simply the first ttinfo structure in the absence of a standard-time
763 // structure) if either tzh_timecnt is zero or the time argument is less
764 // than the first transition time recorded in the file.
767 // ctime(3), time2posix(3), zic(8)
769 // BSD September 13, 1994 BSD
773 // TIME(3) BSD Library Functions Manual TIME(3)
776 // time -- get time of day
779 // Standard C Library (libc, -lc)
785 // time(time_t *tloc);
788 // The time() function returns the value of time in seconds since 0 hours, 0
789 // minutes, 0 seconds, January 1, 1970, Coordinated Universal Time, without
790 // including leap seconds. If an error occurs, time() returns the value
793 // The return value is also stored in *tloc, provided that tloc is non-null.
796 // The time() function may fail for any of the reasons described in
800 // gettimeofday(2), ctime(3)
803 // The time function conforms to IEEE Std 1003.1-2001 (``POSIX.1'').
806 // Neither ISO/IEC 9899:1999 (``ISO C99'') nor IEEE Std 1003.1-2001
807 // (``POSIX.1'') requires time() to set errno on failure; thus, it is impos-
808 // sible for an application to distinguish the valid time value -1 (repre-
809 // senting the last UTC second of 1969) from the error return value.
811 // Systems conforming to earlier versions of the C and POSIX standards
812 // (including older versions of FreeBSD) did not set *tloc in the error
816 // A time() function appeared in Version 6 AT&T UNIX.
818 // BSD July 18, 2003 BSD
821 private static void TZif_GenerateAdjustmentRules(out AdjustmentRule[] rules, TimeSpan baseUtcOffset, DateTime[] dts, byte[] typeOfLocalTime,
822 TZifType[] transitionType, bool[] StandardTime, bool[] GmtTime, string futureTransitionsPosixFormat)
829 List<AdjustmentRule> rulesList = new List<AdjustmentRule>();
831 while (index <= dts.Length)
833 TZif_GenerateAdjustmentRule(ref index, baseUtcOffset, rulesList, dts, typeOfLocalTime, transitionType, StandardTime, GmtTime, futureTransitionsPosixFormat);
836 rules = rulesList.ToArray();
837 if (rules != null && rules.Length == 0)
844 private static void TZif_GenerateAdjustmentRule(ref int index, TimeSpan timeZoneBaseUtcOffset, List<AdjustmentRule> rulesList, DateTime[] dts,
845 byte[] typeOfLocalTime, TZifType[] transitionTypes, bool[] StandardTime, bool[] GmtTime, string futureTransitionsPosixFormat)
847 // To generate AdjustmentRules, use the following approach:
848 // The first AdjustmentRule will go from DateTime.MinValue to the first transition time greater than DateTime.MinValue.
849 // Each middle AdjustmentRule wil go from dts[index-1] to dts[index].
850 // The last AdjustmentRule will go from dts[dts.Length-1] to Datetime.MaxValue.
852 // 0. Skip any DateTime.MinValue transition times. In newer versions of the tzfile, there
853 // is a "big bang" transition time, which is before the year 0001. Since any times before year 0001
854 // cannot be represented by DateTime, there is no reason to make AdjustmentRules for these unrepresentable time periods.
855 // 1. If there are no DateTime.MinValue times, the first AdjustmentRule goes from DateTime.MinValue
856 // to the first transition and uses the first standard transitionType (or the first transitionType if none of them are standard)
857 // 2. Create an AdjustmentRule for each transition, i.e. from dts[index - 1] to dts[index].
858 // This rule uses the transitionType[index - 1] and the whole AdjustmentRule only describes a single offset - either
859 // all daylight savings, or all stanard time.
860 // 3. After all the transitions are filled out, the last AdjustmentRule is created from either:
861 // a. a POSIX-style timezone description ("futureTransitionsPosixFormat"), if there is one or
862 // b. continue the last transition offset until DateTime.Max
864 while (index < dts.Length && dts[index] == DateTime.MinValue)
871 TZifType transitionType = TZif_GetEarlyDateTransitionType(transitionTypes);
872 DateTime endTransitionDate = dts[index];
874 TimeSpan transitionOffset = TZif_CalculateTransitionOffsetFromBase(transitionType.UtcOffset, timeZoneBaseUtcOffset);
875 TimeSpan daylightDelta = transitionType.IsDst ? transitionOffset : TimeSpan.Zero;
876 TimeSpan baseUtcDelta = transitionType.IsDst ? TimeSpan.Zero : transitionOffset;
878 AdjustmentRule r = AdjustmentRule.CreateAdjustmentRule(
880 endTransitionDate.AddTicks(-1),
882 default(TransitionTime),
883 default(TransitionTime),
885 noDaylightTransitions: true);
888 else if (index < dts.Length)
890 DateTime startTransitionDate = dts[index - 1];
891 TZifType startTransitionType = transitionTypes[typeOfLocalTime[index - 1]];
893 DateTime endTransitionDate = dts[index];
895 TimeSpan transitionOffset = TZif_CalculateTransitionOffsetFromBase(startTransitionType.UtcOffset, timeZoneBaseUtcOffset);
896 TimeSpan daylightDelta = startTransitionType.IsDst ? transitionOffset : TimeSpan.Zero;
897 TimeSpan baseUtcDelta = startTransitionType.IsDst ? TimeSpan.Zero : transitionOffset;
899 TransitionTime dstStart;
900 if (startTransitionType.IsDst)
902 // the TransitionTime fields are not used when AdjustmentRule.NoDaylightTransitions == true.
903 // However, there are some cases in the past where DST = true, and the daylight savings offset
904 // now equals what the current BaseUtcOffset is. In that case, the AdjustmentRule.DaylightOffset
905 // is going to be TimeSpan.Zero. But we still need to return 'true' from AdjustmentRule.HasDaylightSaving.
906 // To ensure we always return true from HasDaylightSaving, make a "special" dstStart that will make the logic
907 // in HasDaylightSaving return true.
908 dstStart = TransitionTime.CreateFixedDateRule(DateTime.MinValue.AddMilliseconds(2), 1, 1);
912 dstStart = default(TransitionTime);
915 AdjustmentRule r = AdjustmentRule.CreateAdjustmentRule(
917 endTransitionDate.AddTicks(-1),
920 default(TransitionTime),
922 noDaylightTransitions: true);
927 // create the AdjustmentRule that will be used for all DateTimes after the last transition
929 // NOTE: index == dts.Length
930 DateTime startTransitionDate = dts[index - 1];
932 if (!string.IsNullOrEmpty(futureTransitionsPosixFormat))
934 AdjustmentRule r = TZif_CreateAdjustmentRuleForPosixFormat(futureTransitionsPosixFormat, startTransitionDate, timeZoneBaseUtcOffset);
942 // just use the last transition as the rule which will be used until the end of time
944 TZifType transitionType = transitionTypes[typeOfLocalTime[index - 1]];
945 TimeSpan transitionOffset = TZif_CalculateTransitionOffsetFromBase(transitionType.UtcOffset, timeZoneBaseUtcOffset);
946 TimeSpan daylightDelta = transitionType.IsDst ? transitionOffset : TimeSpan.Zero;
947 TimeSpan baseUtcDelta = transitionType.IsDst ? TimeSpan.Zero : transitionOffset;
949 AdjustmentRule r = AdjustmentRule.CreateAdjustmentRule(
953 default(TransitionTime),
954 default(TransitionTime),
956 noDaylightTransitions: true);
964 private static TimeSpan TZif_CalculateTransitionOffsetFromBase(TimeSpan transitionOffset, TimeSpan timeZoneBaseUtcOffset)
966 TimeSpan result = transitionOffset - timeZoneBaseUtcOffset;
968 // TZif supports seconds-level granularity with offsets but TimeZoneInfo only supports minutes since it aligns
969 // with DateTimeOffset, SQL Server, and the W3C XML Specification
970 if (result.Ticks % TimeSpan.TicksPerMinute != 0)
972 result = new TimeSpan(result.Hours, result.Minutes, 0);
979 /// Gets the first standard-time transition type, or simply the first transition type
980 /// if there are no standard transition types.
983 /// from 'man tzfile':
984 /// localtime(3) uses the first standard-time ttinfo structure in the file
985 /// (or simply the first ttinfo structure in the absence of a standard-time
986 /// structure) if either tzh_timecnt is zero or the time argument is less
987 /// than the first transition time recorded in the file.
989 private static TZifType TZif_GetEarlyDateTransitionType(TZifType[] transitionTypes)
991 foreach (TZifType transitionType in transitionTypes)
993 if (!transitionType.IsDst)
995 return transitionType;
999 if (transitionTypes.Length > 0)
1001 return transitionTypes[0];
1004 throw new InvalidTimeZoneException(SR.InvalidTimeZone_NoTTInfoStructures);
1008 /// Creates an AdjustmentRule given the POSIX TZ environment variable string.
1011 /// See http://man7.org/linux/man-pages/man3/tzset.3.html for the format and semantics of this POSX string.
1013 private static AdjustmentRule TZif_CreateAdjustmentRuleForPosixFormat(string posixFormat, DateTime startTransitionDate, TimeSpan timeZoneBaseUtcOffset)
1015 string standardName;
1016 string standardOffset;
1017 string daylightSavingsName;
1018 string daylightSavingsOffset;
1024 if (TZif_ParsePosixFormat(posixFormat, out standardName, out standardOffset, out daylightSavingsName,
1025 out daylightSavingsOffset, out start, out startTime, out end, out endTime))
1027 // a valid posixFormat has at least standardName and standardOffset
1029 TimeSpan? parsedBaseOffset = TZif_ParseOffsetString(standardOffset);
1030 if (parsedBaseOffset.HasValue)
1032 TimeSpan baseOffset = parsedBaseOffset.Value.Negate(); // offsets are backwards in POSIX notation
1033 baseOffset = TZif_CalculateTransitionOffsetFromBase(baseOffset, timeZoneBaseUtcOffset);
1035 // having a daylightSavingsName means there is a DST rule
1036 if (!string.IsNullOrEmpty(daylightSavingsName))
1038 TimeSpan? parsedDaylightSavings = TZif_ParseOffsetString(daylightSavingsOffset);
1039 TimeSpan daylightSavingsTimeSpan;
1040 if (!parsedDaylightSavings.HasValue)
1042 // default DST to 1 hour if it isn't specified
1043 daylightSavingsTimeSpan = new TimeSpan(1, 0, 0);
1047 daylightSavingsTimeSpan = parsedDaylightSavings.Value.Negate(); // offsets are backwards in POSIX notation
1048 daylightSavingsTimeSpan = TZif_CalculateTransitionOffsetFromBase(daylightSavingsTimeSpan, timeZoneBaseUtcOffset);
1049 daylightSavingsTimeSpan = TZif_CalculateTransitionOffsetFromBase(daylightSavingsTimeSpan, baseOffset);
1052 TransitionTime dstStart = TZif_CreateTransitionTimeFromPosixRule(start, startTime);
1053 TransitionTime dstEnd = TZif_CreateTransitionTimeFromPosixRule(end, endTime);
1055 return AdjustmentRule.CreateAdjustmentRule(
1056 startTransitionDate,
1058 daylightSavingsTimeSpan,
1062 noDaylightTransitions: false);
1066 // if there is no daylightSavingsName, the whole AdjustmentRule should be with no transitions - just the baseOffset
1067 return AdjustmentRule.CreateAdjustmentRule(
1068 startTransitionDate,
1071 default(TransitionTime),
1072 default(TransitionTime),
1074 noDaylightTransitions: true);
1082 private static TimeSpan? TZif_ParseOffsetString(string offset)
1084 TimeSpan? result = null;
1086 if (!string.IsNullOrEmpty(offset))
1088 bool negative = offset[0] == '-';
1089 if (negative || offset[0] == '+')
1091 offset = offset.Substring(1);
1094 // Try parsing just hours first.
1095 // Note, TimeSpan.TryParseExact "%h" can't be used here because some time zones using values
1096 // like "26" or "144" and TimeSpan parsing would turn that into 26 or 144 *days* instead of hours.
1098 if (int.TryParse(offset, out hours))
1100 result = new TimeSpan(hours, 0, 0);
1104 TimeSpan parsedTimeSpan;
1105 if (TimeSpan.TryParseExact(offset, "g", CultureInfo.InvariantCulture, out parsedTimeSpan))
1107 result = parsedTimeSpan;
1111 if (result.HasValue && negative)
1113 result = result.Value.Negate();
1120 private static TransitionTime TZif_CreateTransitionTimeFromPosixRule(string date, string time)
1122 if (string.IsNullOrEmpty(date))
1124 return default(TransitionTime);
1130 // This specifies day d of week w of month m. The day d must be between 0(Sunday) and 6.The week w must be between 1 and 5;
1131 // week 1 is the first week in which day d occurs, and week 5 specifies the last d day in the month. The month m should be between 1 and 12.
1136 if (!TZif_ParseMDateRule(date, out month, out week, out day))
1138 throw new InvalidTimeZoneException(SR.Format(SR.InvalidTimeZone_UnparseablePosixMDateString, date));
1142 TimeSpan? timeOffset = TZif_ParseOffsetString(time);
1143 if (timeOffset.HasValue)
1145 // This logic isn't correct and can't be corrected until https://github.com/dotnet/corefx/issues/2618 is fixed.
1146 // Some time zones use time values like, "26", "144", or "-2".
1147 // This allows the week to sometimes be week 4 and sometimes week 5 in the month.
1148 // For now, strip off any 'days' in the offset, and just get the time of day correct
1149 timeOffset = new TimeSpan(timeOffset.Value.Hours, timeOffset.Value.Minutes, timeOffset.Value.Seconds);
1150 if (timeOffset.Value < TimeSpan.Zero)
1152 timeOfDay = new DateTime(1, 1, 2, 0, 0, 0);
1156 timeOfDay = new DateTime(1, 1, 1, 0, 0, 0);
1159 timeOfDay += timeOffset.Value;
1164 timeOfDay = new DateTime(1, 1, 1, 2, 0, 0);
1167 return TransitionTime.CreateFloatingDateRule(timeOfDay, month, week, day);
1172 // This specifies the Julian day, with n between 1 and 365.February 29 is never counted, even in leap years.
1175 // This specifies the Julian day, with n between 0 and 365.February 29 is counted in leap years.
1177 // These two rules cannot be expressed with the current AdjustmentRules
1178 // One of them *could* be supported if we relaxed the TransitionTime validation rules, and allowed
1179 // "IsFixedDateRule = true, Month = 0, Day = n" to mean the nth day of the year, picking one of the rules above
1181 throw new InvalidTimeZoneException(SR.InvalidTimeZone_JulianDayNotSupported);
1186 /// Parses a string like Mm.w.d into month, week and DayOfWeek values.
1189 /// true if the parsing succeeded; otherwise, false.
1191 private static bool TZif_ParseMDateRule(string dateRule, out int month, out int week, out DayOfWeek dayOfWeek)
1193 if (dateRule[0] == 'M')
1195 int firstDotIndex = dateRule.IndexOf('.');
1196 if (firstDotIndex > 0)
1198 int secondDotIndex = dateRule.IndexOf('.', firstDotIndex + 1);
1199 if (secondDotIndex > 0)
1201 if (int.TryParse(dateRule.AsSpan(1, firstDotIndex - 1), out month) &&
1202 int.TryParse(dateRule.AsSpan(firstDotIndex + 1, secondDotIndex - firstDotIndex - 1), out week) &&
1203 int.TryParse(dateRule.AsSpan(secondDotIndex + 1), out int day))
1205 dayOfWeek = (DayOfWeek)day;
1214 dayOfWeek = default(DayOfWeek);
1218 private static bool TZif_ParsePosixFormat(
1220 out string standardName,
1221 out string standardOffset,
1222 out string daylightSavingsName,
1223 out string daylightSavingsOffset,
1225 out string startTime,
1229 standardName = null;
1230 standardOffset = null;
1231 daylightSavingsName = null;
1232 daylightSavingsOffset = null;
1239 standardName = TZif_ParsePosixName(posixFormat, ref index);
1240 standardOffset = TZif_ParsePosixOffset(posixFormat, ref index);
1242 daylightSavingsName = TZif_ParsePosixName(posixFormat, ref index);
1243 if (!string.IsNullOrEmpty(daylightSavingsName))
1245 daylightSavingsOffset = TZif_ParsePosixOffset(posixFormat, ref index);
1247 if (index < posixFormat.Length && posixFormat[index] == ',')
1250 TZif_ParsePosixDateTime(posixFormat, ref index, out start, out startTime);
1252 if (index < posixFormat.Length && posixFormat[index] == ',')
1255 TZif_ParsePosixDateTime(posixFormat, ref index, out end, out endTime);
1260 return !string.IsNullOrEmpty(standardName) && !string.IsNullOrEmpty(standardOffset);
1263 private static string TZif_ParsePosixName(string posixFormat, ref int index)
1265 bool isBracketEnclosed = index < posixFormat.Length && posixFormat[index] == '<';
1266 if (isBracketEnclosed)
1268 // move past the opening bracket
1271 string result = TZif_ParsePosixString(posixFormat, ref index, c => c == '>');
1273 // move past the closing bracket
1274 if (index < posixFormat.Length && posixFormat[index] == '>')
1283 return TZif_ParsePosixString(
1286 c => char.IsDigit(c) || c == '+' || c == '-' || c == ',');
1290 private static string TZif_ParsePosixOffset(string posixFormat, ref int index) =>
1291 TZif_ParsePosixString(posixFormat, ref index, c => !char.IsDigit(c) && c != '+' && c != '-' && c != ':');
1293 private static void TZif_ParsePosixDateTime(string posixFormat, ref int index, out string date, out string time)
1297 date = TZif_ParsePosixDate(posixFormat, ref index);
1298 if (index < posixFormat.Length && posixFormat[index] == '/')
1301 time = TZif_ParsePosixTime(posixFormat, ref index);
1305 private static string TZif_ParsePosixDate(string posixFormat, ref int index) =>
1306 TZif_ParsePosixString(posixFormat, ref index, c => c == '/' || c == ',');
1308 private static string TZif_ParsePosixTime(string posixFormat, ref int index) =>
1309 TZif_ParsePosixString(posixFormat, ref index, c => c == ',');
1311 private static string TZif_ParsePosixString(string posixFormat, ref int index, Func<char, bool> breakCondition)
1313 int startIndex = index;
1314 for (; index < posixFormat.Length; index++)
1316 char current = posixFormat[index];
1317 if (breakCondition(current))
1323 return posixFormat.Substring(startIndex, index - startIndex);
1326 // Returns the Substring from zoneAbbreviations starting at index and ending at '\0'
1327 // zoneAbbreviations is expected to be in the form: "PST\0PDT\0PWT\0\PPT"
1328 private static string TZif_GetZoneAbbreviation(string zoneAbbreviations, int index)
1330 int lastIndex = zoneAbbreviations.IndexOf('\0', index);
1331 return lastIndex > 0 ?
1332 zoneAbbreviations.Substring(index, lastIndex - index) :
1333 zoneAbbreviations.Substring(index);
1336 // Converts an array of bytes into an int - always using standard byte order (Big Endian)
1337 // per TZif file standard
1338 private static unsafe int TZif_ToInt32(byte[] value, int startIndex)
1340 fixed (byte* pbyte = &value[startIndex])
1342 return (*pbyte << 24) | (*(pbyte + 1) << 16) | (*(pbyte + 2) << 8) | (*(pbyte + 3));
1346 // Converts an array of bytes into a long - always using standard byte order (Big Endian)
1347 // per TZif file standard
1348 private static unsafe long TZif_ToInt64(byte[] value, int startIndex)
1350 fixed (byte* pbyte = &value[startIndex])
1352 int i1 = (*pbyte << 24) | (*(pbyte + 1) << 16) | (*(pbyte + 2) << 8) | (*(pbyte + 3));
1353 int i2 = (*(pbyte + 4) << 24) | (*(pbyte + 5) << 16) | (*(pbyte + 6) << 8) | (*(pbyte + 7));
1354 return (uint)i2 | ((long)i1 << 32);
1358 private static long TZif_ToUnixTime(byte[] value, int startIndex, TZVersion version) =>
1359 version != TZVersion.V1 ?
1360 TZif_ToInt64(value, startIndex) :
1361 TZif_ToInt32(value, startIndex);
1363 private static DateTime TZif_UnixTimeToDateTime(long unixTime) =>
1364 unixTime < DateTimeOffset.UnixMinSeconds ? DateTime.MinValue :
1365 unixTime > DateTimeOffset.UnixMaxSeconds ? DateTime.MaxValue :
1366 DateTimeOffset.FromUnixTimeSeconds(unixTime).UtcDateTime;
1368 private static void TZif_ParseRaw(byte[] data, out TZifHead t, out DateTime[] dts, out byte[] typeOfLocalTime, out TZifType[] transitionType,
1369 out string zoneAbbreviations, out bool[] StandardTime, out bool[] GmtTime, out string futureTransitionsPosixFormat)
1371 // initialize the out parameters in case the TZifHead ctor throws
1373 typeOfLocalTime = null;
1374 transitionType = null;
1375 zoneAbbreviations = string.Empty;
1376 StandardTime = null;
1378 futureTransitionsPosixFormat = null;
1380 // read in the 44-byte TZ header containing the count/length fields
1383 t = new TZifHead(data, index);
1384 index += TZifHead.Length;
1386 int timeValuesLength = 4; // the first version uses 4-bytes to specify times
1387 if (t.Version != TZVersion.V1)
1389 // move index past the V1 information to read the V2 information
1390 index += (int)((timeValuesLength * t.TimeCount) + t.TimeCount + (6 * t.TypeCount) + ((timeValuesLength + 4) * t.LeapCount) + t.IsStdCount + t.IsGmtCount + t.CharCount);
1392 // read the V2 header
1393 t = new TZifHead(data, index);
1394 index += TZifHead.Length;
1395 timeValuesLength = 8; // the second version uses 8-bytes
1398 // initialize the containers for the rest of the TZ data
1399 dts = new DateTime[t.TimeCount];
1400 typeOfLocalTime = new byte[t.TimeCount];
1401 transitionType = new TZifType[t.TypeCount];
1402 zoneAbbreviations = string.Empty;
1403 StandardTime = new bool[t.TypeCount];
1404 GmtTime = new bool[t.TypeCount];
1406 // read in the UTC transition points and convert them to Windows
1408 for (int i = 0; i < t.TimeCount; i++)
1410 long unixTime = TZif_ToUnixTime(data, index, t.Version);
1411 dts[i] = TZif_UnixTimeToDateTime(unixTime);
1412 index += timeValuesLength;
1415 // read in the Type Indices; there is a 1:1 mapping of UTC transition points to Type Indices
1416 // these indices directly map to the array index in the transitionType array below
1418 for (int i = 0; i < t.TimeCount; i++)
1420 typeOfLocalTime[i] = data[index];
1424 // read in the Type table. Each 6-byte entry represents
1425 // {UtcOffset, IsDst, AbbreviationIndex}
1427 // each AbbreviationIndex is a character index into the zoneAbbreviations string below
1429 for (int i = 0; i < t.TypeCount; i++)
1431 transitionType[i] = new TZifType(data, index);
1435 // read in the Abbreviation ASCII string. This string will be in the form:
1436 // "PST\0PDT\0PWT\0\PPT"
1438 Encoding enc = Encoding.UTF8;
1439 zoneAbbreviations = enc.GetString(data, index, (int)t.CharCount);
1440 index += (int)t.CharCount;
1442 // skip ahead of the Leap-Seconds Adjustment data. In a future release, consider adding
1443 // support for Leap-Seconds
1445 index += (int)(t.LeapCount * (timeValuesLength + 4)); // skip the leap second transition times
1447 // read in the Standard Time table. There should be a 1:1 mapping between Type-Index and Standard
1448 // Time table entries.
1450 // TRUE = transition time is standard time
1451 // FALSE = transition time is wall clock time
1452 // ABSENT = transition time is wall clock time
1454 for (int i = 0; i < t.IsStdCount && i < t.TypeCount && index < data.Length; i++)
1456 StandardTime[i] = (data[index++] != 0);
1459 // read in the GMT Time table. There should be a 1:1 mapping between Type-Index and GMT Time table
1462 // TRUE = transition time is UTC
1463 // FALSE = transition time is local time
1464 // ABSENT = transition time is local time
1466 for (int i = 0; i < t.IsGmtCount && i < t.TypeCount && index < data.Length; i++)
1468 GmtTime[i] = (data[index++] != 0);
1471 if (t.Version != TZVersion.V1)
1473 // read the POSIX-style format, which should be wrapped in newlines with the last newline at the end of the file
1474 if (data[index++] == '\n' && data[data.Length - 1] == '\n')
1476 futureTransitionsPosixFormat = enc.GetString(data, index, data.Length - index - 1);
1481 private struct TZifType
1483 public const int Length = 6;
1485 public readonly TimeSpan UtcOffset;
1486 public readonly bool IsDst;
1487 public readonly byte AbbreviationIndex;
1489 public TZifType(byte[] data, int index)
1491 if (data == null || data.Length < index + Length)
1493 throw new ArgumentException(SR.Argument_TimeZoneInfoInvalidTZif, nameof(data));
1495 UtcOffset = new TimeSpan(0, 0, TZif_ToInt32(data, index + 00));
1496 IsDst = (data[index + 4] != 0);
1497 AbbreviationIndex = data[index + 5];
1501 private struct TZifHead
1503 public const int Length = 44;
1505 public readonly uint Magic; // TZ_MAGIC "TZif"
1506 public readonly TZVersion Version; // 1 byte for a \0 or 2 or 3
1507 // public byte[15] Reserved; // reserved for future use
1508 public readonly uint IsGmtCount; // number of transition time flags
1509 public readonly uint IsStdCount; // number of transition time flags
1510 public readonly uint LeapCount; // number of leap seconds
1511 public readonly uint TimeCount; // number of transition times
1512 public readonly uint TypeCount; // number of local time types
1513 public readonly uint CharCount; // number of abbreviated characters
1515 public TZifHead(byte[] data, int index)
1517 if (data == null || data.Length < Length)
1519 throw new ArgumentException("bad data", nameof(data));
1522 Magic = (uint)TZif_ToInt32(data, index + 00);
1524 if (Magic != 0x545A6966)
1526 // 0x545A6966 = {0x54, 0x5A, 0x69, 0x66} = "TZif"
1527 throw new ArgumentException(SR.Argument_TimeZoneInfoBadTZif, nameof(data));
1530 byte version = data[index + 04];
1532 version == '2' ? TZVersion.V2 :
1533 version == '3' ? TZVersion.V3 :
1534 TZVersion.V1; // default/fallback to V1 to guard against future, unsupported version numbers
1536 // skip the 15 byte reserved field
1538 // don't use the BitConverter class which parses data
1539 // based on the Endianess of the machine architecture.
1540 // this data is expected to always be in "standard byte order",
1541 // regardless of the machine it is being processed on.
1543 IsGmtCount = (uint)TZif_ToInt32(data, index + 20);
1544 IsStdCount = (uint)TZif_ToInt32(data, index + 24);
1545 LeapCount = (uint)TZif_ToInt32(data, index + 28);
1546 TimeCount = (uint)TZif_ToInt32(data, index + 32);
1547 TypeCount = (uint)TZif_ToInt32(data, index + 36);
1548 CharCount = (uint)TZif_ToInt32(data, index + 40);
1552 private enum TZVersion : byte
1557 // when adding more versions, ensure all the logic using TZVersion is still correct