Date and Time Functions calendrical calculations and miscellaneous time stuff. The #GDate data structure represents a day between January 1, Year 1, and sometime a few thousand years in the future (right now it will go to the year 65535 or so, but g_date_set_parse() only parses up to the year 8000 or so - just count on "a few thousand"). #GDate is meant to represent everyday dates, not astronomical dates or historical dates or ISO timestamps or the like. It extrapolates the current Gregorian calendar forward and backward in time; there is no attempt to change the calendar to match time periods or locations. #GDate does not store time information; it represents a day. The #GDate implementation has several nice features; it is only a 64-bit struct, so storing large numbers of dates is very efficient. It can keep both a Julian and day-month-year representation of the date, since some calculations are much easier with one representation or the other. A Julian representation is simply a count of days since some fixed day in the past; for #GDate the fixed day is January 1, 1 AD. ("Julian" dates in the #GDate API aren't really Julian dates in the technical sense; technically, Julian dates count from the start of the Julian period, Jan 1, 4713 BC). #GDate is simple to use. First you need a "blank" date; you can get a dynamically allocated date from g_date_new(), or you can declare an automatic variable or array and initialize it to a sane state by calling g_date_clear(). A cleared date is sane; it's safe to call g_date_set_dmy() and the other mutator functions to initialize the value of a cleared date. However, a cleared date is initially invalid, meaning that it doesn't represent a day that exists. It is undefined to call any of the date calculation routines on an invalid date. If you obtain a date from a user or other unpredictable source, you should check its validity with the g_date_valid() predicate. g_date_valid() is also used to check for errors with g_date_set_parse() and other functions that can fail. Dates can be invalidated by calling g_date_clear() again. It is very important to use the API to access the #GDate struct. Often only the day-month-year or only the Julian representation is valid. Sometimes neither is valid. Use the API. GLib doesn't contain any time-manipulation functions; however, there is a #GTime typedef which is equivalent to time_t, and a #GTimeVal struct which represents a more precise time (with microseconds). You can request the current time as a #GTimeVal with g_get_current_time(). Number of microseconds in one second (1 million). This macro is provided for code readability. Represents a precise time, with seconds and microseconds. Same as the struct timeval returned by the gettimeofday() UNIX call. @tv_sec: seconds. @tv_usec: microseconds. @result: Pauses the current thread for the given number of microseconds. There are 1 million microseconds per second (represented by the #G_USEC_PER_SEC macro). g_usleep() may have limited precision, depending on hardware and operating system; don't rely on the exact length of the sleep. @microseconds: number of microseconds to pause. @time_: @microseconds: Represents a day between January 1, Year 1 and a few thousand years in the future. None of its members should be accessed directly. If the GDate is obtained from g_date_new(), it will be safe to mutate but invalid and thus not safe for calendrical computations. If it's declared on the stack, it will contain garbage so must be initialized with g_date_clear(). g_date_clear() makes the date invalid but sane. An invalid date doesn't represent a day, it's "empty." A date becomes valid after you set it to a Julian day or you set a day, month, and year. @julian_days: the Julian representation of the date @julian: this bit is set if @julian_days is valid @dmy: this is set if @day, @month and @year are valid @day: the day of the day-month-year representation of the date, as a number between 1 and 31 @month: the day of the day-month-year representation of the date, as a number between 1 and 12 @year: the day of the day-month-year representation of the date Simply a replacement for time_t. Unrelated to #GTimer. This enumeration isn't used in the API, but may be useful if you need to mark a number as a day, month, or year. @G_DATE_DAY: a day @G_DATE_MONTH: a month @G_DATE_YEAR: a year Integer representing a day of the month; between 1 and 31. #G_DATE_BAD_DAY represents an invalid day of the month. Enumeration representing a month; values are #G_DATE_JANUARY, #G_DATE_FEBRUARY, etc. #G_DATE_BAD_MONTH is the invalid value. @G_DATE_BAD_MONTH: invalid value. @G_DATE_JANUARY: January. @G_DATE_FEBRUARY: February. @G_DATE_MARCH: March. @G_DATE_APRIL: April. @G_DATE_MAY: May. @G_DATE_JUNE: June. @G_DATE_JULY: July. @G_DATE_AUGUST: August. @G_DATE_SEPTEMBER: September. @G_DATE_OCTOBER: October. @G_DATE_NOVEMBER: November. @G_DATE_DECEMBER: December. Integer representing a year; #G_DATE_BAD_YEAR is the invalid value. The year must be 1 or higher; negative (BC) years are not allowed. The year is represented with four digits. Enumeration representing a day of the week; #G_DATE_MONDAY, #G_DATE_TUESDAY, etc. #G_DATE_BAD_WEEKDAY is an invalid weekday. @G_DATE_BAD_WEEKDAY: invalid value. @G_DATE_MONDAY: Monday. @G_DATE_TUESDAY: Tuesday. @G_DATE_WEDNESDAY: Wednesday. @G_DATE_THURSDAY: Thursday. @G_DATE_FRIDAY: Friday. @G_DATE_SATURDAY: Saturday. @G_DATE_SUNDAY: Sunday. Represents an invalid #GDateDay. Represents an invalid Julian day number. Represents an invalid year. Allocates a #GDate and initializes it to a sane state. The new date will be cleared (as if you'd called g_date_clear()) but invalid (it won't represent an existing day). Free the return value with g_date_free(). @Returns: a newly-allocated #GDate. Like g_date_new(), but also sets the value of the date. Assuming the day-month-year triplet you pass in represents an existing day, the returned date will be valid. @day: day of the month. @month: month of the year. @year: year @Returns: a newly-allocated #GDate initialized with @day, @month, and @year. Like g_date_new(), but also sets the value of the date. Assuming the Julian day number you pass in is valid (greater than 0, less than an unreasonably large number), the returned date will be valid. @julian_day: days since January 1, Year 1. @Returns: a newly-allocated #GDate initialized with @julian_day. Initializes one or more #GDate structs to a sane but invalid state. The cleared dates will not represent an existing date, but will not contain garbage. Useful to init a date declared on the stack. Validity can be tested with g_date_valid(). @date: pointer to one or more dates to clear. @n_dates: number of dates to clear. Frees a #GDate returned from g_date_new(). @date: a #GDate. Sets the day of the month for a #GDate. If the resulting day-month-year triplet is invalid, the date will be invalid. @date: a #GDate. @day: day to set. Sets the month of the year for a #GDate. If the resulting day-month-year triplet is invalid, the date will be invalid. @date: a #GDate. @month: month to set. Sets the year for a #GDate. If the resulting day-month-year triplet is invalid, the date will be invalid. @date: a #GDate. @year: year to set. Sets the value of a #GDate from a day, month, and year. The day-month-year triplet must be valid; if you aren't sure it is, call g_date_valid_dmy() to check before you set it. @date: a #GDate. @day: day. @month: month. @y: year. Sets the value of a #GDate from a Julian day number. @date: a #GDate. @julian_date: Julian day number (days since January 1, Year 1). Sets the value of a date from a #GTime (time_t) value. To set the value of a date to the current day, you could write: g_date_set_time (date, time (NULL)); @date: a #GDate. @time_: #GTime value to set. Parses a user-inputted string @str, and try to figure out what date it represents, taking the current locale into account. If the string is successfully parsed, the date will be valid after the call. Otherwise, it will be invalid. You should check using g_date_valid() to see whether the parsing succeeded. This function is not appropriate for file formats and the like; it isn't very precise, and its exact behavior varies with the locale. It's intended to be a heuristic routine that guesses what the user means by a given string (and it does work pretty well in that capacity). @date: a #GDate to fill in. @str: string to parse. Increments a date some number of days. To move forward by weeks, add weeks*7 days. The date must be valid. @date: a #GDate to increment. @n_days: number of days to move the date forward. Moves a date some number of days into the past. To move by weeks, just move by weeks*7 days. The date must be valid. @date: a #GDate to decrement. @n_days: number of days to move. Increments a date by some number of months. If the day of the month is greater than 28, this routine may change the day of the month (because the destination month may not have the current day in it). The date must be valid. @date: a #GDate to increment. @n_months: number of months to move forward. Moves a date some number of months into the past. If the current day of the month doesn't exist in the destination month, the day of the month may change. The date must be valid. @date: a #GDate to decrement. @n_months: number of months to move. Increments a date by some number of years. If the date is February 29, and the destination year is not a leap year, the date will be changed to February 28. The date must be valid. @date: a #GDate to increment. @n_years: number of years to move forward. Moves a date some number of years into the past. If the current day doesn't exist in the destination year (i.e. it's February 29 and you move to a non-leap-year) then the day is changed to February 29. The date must be valid. @date: a #GDate to decrement. @n_years: number of years to move. Computes the number of days between two dates. If @date2 is prior to @date1, the returned value is negative. Both dates must be valid. @date1: the first date. @date2: the second date. @Returns: the number of days between @date1 and @date2. qsort()-style comparsion function for dates. Both dates must be valid. @lhs: first date to compare. @rhs: second date to compare. @Returns: 0 for equal, less than zero if @lhs is less than @rhs, greater than zero if @lhs is greater than @rhs. If @date is prior to @min_date, sets @date equal to @min_date. If @date falls after @max_date, sets @date equal to @max_date. Either @min_date and @max_date may be %NULL. All non-%NULL dates must be valid. @date: a #GDate to clamp. @min_date: minimum accepted value for @date. @max_date: maximum accepted value for @date. Checks if @date1 is less than or equal to @date2, and swap the values if this is not the case. @date1: the first date. @date2: the second date. Returns the day of the month. The date must be valid. @date: a #GDate to extract the day of the month from. @Returns: day of the month. Returns the month of the year. The date must be valid. @date: a #GDate to get the month from. @Returns: month of the year as a #GDateMonth. Returns the year of a #GDate. The date must be valid. @date: a #GDate. @Returns: year in which the date falls. Returns the Julian day or "serial number" of the #GDate. The Julian day is simply the number of days since January 1, Year 1; i.e., January 1, Year 1 is Julian day 1; January 2, Year 1 is Julian day 2, etc. The date must be valid. @date: a #GDate to extract the Julian day from. @Returns: Julian day. Returns the day of the week for a #GDate. The date must be valid. @date: a #GDate. @Returns: day of the week as a #GDateWeekday. Returns the day of the year, where Jan 1 is the first day of the year. The date must be valid. @date: a #GDate to extract day of year from. @Returns: day of the year. Returns the number of days in a month, taking leap years into account. @month: month. @year: year. @Returns: number of days in @month during the @year. Returns %TRUE if the date is on the first of a month. The date must be valid. @date: a #GDate to check. @Returns: %TRUE if the date is the first of the month. Returns %TRUE if the date is the last day of the month. The date must be valid. @date: a #GDate to check. @Returns: %TRUE if the date is the last day of the month. Returns %TRUE if the year is a leap year. @year: year to check. @Returns: %TRUE if the year is a leap year. Returns the week of the year, where weeks are understood to start on Monday. If the date is before the first Monday of the year, return 0. The date must be valid. @date: a #GDate. @Returns: week of the year. Returns the number of weeks in the year, where weeks are taken to start on Monday. Will be 52 or 53. The date must be valid. (Years always have 52 7-day periods, plus 1 or 2 extra days depending on whether it's a leap year. This function is basically telling you how many Mondays are in the year, i.e. there are 53 Mondays if one of the extra days happens to be a Monday.) @year: a year. @Returns: number of Mondays in the year. Returns the week of the year during which this date falls, if weeks are understood to being on Sunday. The date must be valid. Can return 0 if the day is before the first Sunday of the year. @date: a #GDate. @Returns: week number. Returns the number of weeks in the year, where weeks are taken to start on Sunday. Will be 52 or 53. The date must be valid. (Years always have 52 7-day periods, plus 1 or 2 extra days depending on whether it's a leap year. This function is basically telling you how many Sundays are in the year, i.e. there are 53 Sundays if one of the extra days happens to be a Sunday.) @year: year to count weeks in. @Returns: number of weeks. @date: @Returns: Generates a printed representation of the date, in a locale-specific way. Works just like the standard C strftime() function, but only accepts date-related formats; time-related formats give undefined results. Date must be valid. @s: destination buffer. @slen: buffer size. @format: format string. @date: valid #GDate. @Returns: number of characters written to the buffer, or 0 the buffer was too small. Fills in the date-related bits of a struct tm using the @date value. Initializes the non-date parts with something sane but meaningless. @date: a #GDate to set the struct tm from. @tm: struct tm to fill. Returns %TRUE if the #GDate represents an existing day. The date must not contain garbage; it should have been initialized with g_date_clear() if it wasn't allocated by one of the g_date_new() variants. @date: a #GDate to check. @Returns: Whether the date is valid. Returns %TRUE if the day of the month is valid (a day is valid if it's between 1 and 31 inclusive). @day: day to check. @Returns: %TRUE if the day is valid. Returns %TRUE if the month value is valid. The 12 #GDateMonth enumeration values are the only valid months. @month: month. @Returns: %TRUE if the month is valid. Returns %TRUE if the year is valid. Any year greater than 0 is valid, though there is a 16-bit limit to what #GDate will understand. @year: year. @Returns: %TRUE if the year is valid. Returns %TRUE if the day-month-year triplet forms a valid, existing day in the range of days #GDate understands (Year 1 or later, no more than a few thousand years in the future). @day: day. @month: month. @year: year. @Returns: %TRUE if the date is a valid one. Returns %TRUE if the Julian day is valid. Anything greater than zero is basically a valid Julian, though there is a 32-bit limit. @julian_date: Julian day to check. @Returns: %TRUE if the Julian day is valid. Returns %TRUE if the weekday is valid. The 7 #GDateWeekday enumeration values are the only valid weekdays. @weekday: weekday. @Returns: %TRUE if the weekday is valid.