Date

class Date(**kwargs)

GDate is a struct for calendrical calculations.

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 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 Date the fixed day is January 1, 1 AD. (“Julian” dates in the Date 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 new, or you can declare an automatic variable or array and initialize it by calling clear. A cleared date is safe; it’s safe to call 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 valid predicate. valid is also used to check for errors with set_parse and other functions that can fail. Dates can be invalidated by calling 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 also features GDateTime which represents a precise time.

Constructors

class Date

classmethod new() → Date

Allocates a Date and initializes it to a safe state. The new date will be cleared (as if you’d called clear()) but invalid (it won’t represent an existing day). Free the return value with free().

classmethod new_dmy(day: int, month: DateMonth, year: int) → Date

Create a new Date representing the given day-month-year triplet.

The triplet you pass in must represent a valid date. Use valid_dmy() if needed to validate it. The returned Date is guaranteed to be non-None and valid.

Parameters:

• day – day of the month

• month – month of the year

• year – year

classmethod new_julian(julian_day: int) → Date

Create a new Date representing the given Julian date.

The julian_day you pass in must be valid. Use valid_julian() if needed to validate it. The returned Date is guaranteed to be non-None and valid.

Parameters:

julian_day – days since January 1, Year 1

Methods

class Date

add_days(n_days: int) → None

Increments a date some number of days. To move forward by weeks, add weeks*7 days. The date must be valid.

Parameters:

n_days – number of days to move the date forward

add_months(n_months: int) → None

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.

Parameters:

n_months – number of months to move forward

add_years(n_years: int) → None

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.

Parameters:

n_years – number of years to move forward

clamp(min_date: Date, max_date: Date) → None

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. Otherwise, date is unchanged. Either of min_date and max_date may be None. All non-None dates must be valid.

Parameters:

• min_date – minimum accepted value for date

• max_date – maximum accepted value for date

clear(n_dates: int) → None

Initializes one or more Date structs to a safe 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 valid().

Parameters:

n_dates – number of dates to clear

compare(rhs: Date) → int

qsort()-style comparison function for dates. Both dates must be valid.

Parameters:

rhs – second date to compare

days_between(date2: Date) → int

Computes the number of days between two dates. If date2 is prior to date1, the returned value is negative. Both dates must be valid.

Parameters:

date2 – the second date

free() → None

Frees a Date returned from new().

get_day() → int

Returns the day of the month. The date must be valid.

get_day_of_year() → int

Returns the day of the year, where Jan 1 is the first day of the year. The date must be valid.

get_days_in_month(month: DateMonth, year: int) → int

Returns the number of days in a month, taking leap years into account.

Parameters:

• month – month

• year – year

get_iso8601_week_of_year() → int

Returns the week of the year, where weeks are interpreted according to ISO 8601.

Added in version 2.6.

get_julian() → int

Returns the Julian day or “serial number” of the Date. 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.

get_monday_week_of_year() → int

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.

get_monday_weeks_in_year(year: int) → int

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.)

Parameters:

year – a year

get_month() → DateMonth

Returns the month of the year. The date must be valid.

get_sunday_week_of_year() → int

Returns the week of the year during which this date falls, if weeks are understood to begin on Sunday. The date must be valid. Can return 0 if the day is before the first Sunday of the year.

get_sunday_weeks_in_year(year: int) → int

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.)

Parameters:

year – year to count weeks in

get_weekday() → DateWeekday

Returns the day of the week for a Date. The date must be valid.

get_year() → int

Returns the year of a Date. The date must be valid.

is_first_of_month() → bool

Returns True if the date is on the first of a month. The date must be valid.

is_last_of_month() → bool

Returns True if the date is the last day of the month. The date must be valid.

is_leap_year(year: int) → bool

Returns True if the year is a leap year.

For the purposes of this function, leap year is every year divisible by 4 unless that year is divisible by 100. If it is divisible by 100 it would be a leap year only if that year is also divisible by 400.

Parameters:

year – year to check

order(date2: Date) → None

Checks if date1 is less than or equal to date2, and swap the values if this is not the case.

Parameters:

date2 – the second date

set_day(day: int) → None

Sets the day of the month for a Date. If the resulting day-month-year triplet is invalid, the date will be invalid.

Parameters:

day – day to set

set_dmy(day: int, month: DateMonth, y: int) → None

Sets the value of a Date from a day, month, and year. The day-month-year triplet must be valid; if you aren’t sure it is, call valid_dmy() to check before you set it.

Parameters:

• day – day

• month – month

• y – year

set_julian(julian_date: int) → None

Sets the value of a Date from a Julian day number.

Parameters:

julian_date – Julian day number (days since January 1, Year 1)

set_month(month: DateMonth) → None

Sets the month of the year for a Date. If the resulting day-month-year triplet is invalid, the date will be invalid.

Parameters:

month – month to set

set_parse(str: str) → None

Parses a user-inputted string str, and try to figure out what date it represents, taking the [current locale][setlocale] 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 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).

Parameters:

str – string to parse

set_time(time_: int) → None

Sets the value of a date from a Time value. The time to date conversion is done using the user’s current timezone.

Deprecated since version 2.10: Use set_time_t() instead.

Parameters:

time – Time value to set.

set_time_t(timet: int) → None

Sets the value of a date to the date corresponding to a time specified as a time_t. The time to date conversion is done using the user’s current timezone.

To set the value of a date to the current day, you could write:

time_t now = time (NULL);
if (now == (time_t) -1)
  // handle the error
g_date_set_time_t (date, now);

Added in version 2.10.

Parameters:

timet – time_t value to set

set_time_val(timeval: TimeVal) → None

Sets the value of a date from a TimeVal value. Note that the tv_usec member is ignored, because Date can’t make use of the additional precision.

The time to date conversion is done using the user’s current timezone.

Added in version 2.10.

Deprecated since version 2.62: TimeVal is not year-2038-safe. Use set_time_t() instead.

Parameters:

timeval – TimeVal value to set

set_year(year: int) → None

Sets the year for a Date. If the resulting day-month-year triplet is invalid, the date will be invalid.

Parameters:

year – year to set

strftime(s: str, slen: int, format: str, date: Date) → int

Generates a printed representation of the date, in a [locale][setlocale]-specific way. Works just like the platform’s C library strftime() function, but only accepts date-related formats; time-related formats give undefined results. Date must be valid. Unlike strftime() (which uses the locale encoding), works on a UTF-8 format string and stores a UTF-8 result.

This function does not provide any conversion specifiers in addition to those implemented by the platform’s C library. For example, don’t expect that using strftime() would make the ``%F`` provided by the C99 strftime() work on Windows where the C library only complies to C89.

Parameters:

• s – destination buffer

• slen – buffer size

• format – format string

• date – valid Date

subtract_days(n_days: int) → None

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.

Parameters:

n_days – number of days to move

subtract_months(n_months: int) → None

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.

Parameters:

n_months – number of months to move

subtract_years(n_years: int) → None

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.

Parameters:

n_years – number of years to move

to_struct_tm(tm: None) → None

Fills in the date-related bits of a struct tm using the date value. Initializes the non-date parts with something safe but meaningless.

Parameters:

tm – struct tm to fill

valid() → bool

Returns True if the Date represents an existing day. The date must not contain garbage; it should have been initialized with clear() if it wasn’t allocated by one of the new() variants.

valid_day(day: int) → bool

Returns True if the day of the month is valid (a day is valid if it’s between 1 and 31 inclusive).

Parameters:

day – day to check

valid_dmy(day: int, month: DateMonth, year: int) → bool

Returns True if the day-month-year triplet forms a valid, existing day in the range of days Date understands (Year 1 or later, no more than a few thousand years in the future).

Parameters:

• day – day

• month – month

• year – year

valid_julian(julian_date: int) → bool

Returns True if the Julian day is valid. Anything greater than zero is basically a valid Julian, though there is a 32-bit limit.

Parameters:

julian_date – Julian day to check

valid_month(month: DateMonth) → bool

Returns True if the month value is valid. The 12 DateMonth enumeration values are the only valid months.

Parameters:

month – month

valid_weekday(weekday: DateWeekday) → bool

Returns True if the weekday is valid. The seven DateWeekday enumeration values are the only valid weekdays.

Parameters:

weekday – weekday

valid_year(year: int) → bool

Returns True if the year is valid. Any year greater than 0 is valid, though there is a 16-bit limit to what Date will understand.

Parameters:

year – year

Fields

class Date

day

The day of the day-month-year representation of the date, as a number between 1 and 31

dmy

This is set if day, month and year are valid

julian

This bit is set if julian_days is valid

julian_days

The Julian representation of the date

month

The month of the day-month-year representation of the date, as a number between 1 and 12

year

The year of the day-month-year representation of the date