<GDate>

<GDate>

Description

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-struct 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 safe. 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.

Functions

add-days

(define-values () (date:add-days self n-days))

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

Parameters

date

a GDate to increment

Passed as self

n_days

number of days to move the date forward

Passed as n-days

add-months

(define-values () (date:add-months self n-months))

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

date

a GDate to increment

Passed as self

n_months

number of months to move forward

Passed as n-months

add-years

(define-values () (date:add-years self n-years))

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

date

a GDate to increment

Passed as self

n_years

number of years to move forward

Passed as n-years

clamp

(define-values () (date:clamp self min-date max-date))

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 NULL. All non-NULL dates must be valid.

Parameters

date

a GDate to clamp

Passed as self

min_date

minimum accepted value for date

Passed as min-date

max_date

maximum accepted value for date

Passed as max-date

clear

(define-values () (date:clear self n-dates))

Initializes one or more GDate 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 g_date_valid().

Parameters

date

pointer to one or more dates to clear

Passed as self

n_dates

number of dates to clear

Passed as n-dates

compare

(define-values (%return) (date:compare self rhs))

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

Parameters

lhs

first date to compare

Passed as self

rhs

second date to compare

Passed as rhs

copy

(define-values (%return) (date:copy self))

Copies a GDate to a newly-allocated GDate. If the input was invalid (as determined by g_date_valid()), the invalid state will be copied as is into the new object.

Parameters

date

a GDate to copy

Passed as self

days-between

(define-values (%return) (date:days-between self date2))

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

date1

the first date

Passed as self

date2

the second date

Passed as date2

free

(define-values () (date:free self))

Frees a GDate returned from g_date_new().

Parameters

date

a GDate to free

Passed as self

get-day

(define-values (%return) (date:get-day self))

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

Parameters

date

a GDate to extract the day of the month from

Passed as self

get-day-of-year

(define-values (%return) (date:get-day-of-year self))

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

Parameters

date

a GDate to extract day of year from

Passed as self

get-iso8601-week-of-year

(define-values (%return) (date:get-iso8601-week-of-year self))

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

Parameters

date

a valid GDate

Passed as self

get-julian

(define-values (%return) (date:get-julian self))

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.

Parameters

date

a GDate to extract the Julian day from

Passed as self

get-monday-week-of-year

(define-values (%return) (date:get-monday-week-of-year self))

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.

Parameters

date

a GDate

Passed as self

get-month

(define-values (%return) (date:get-month self))

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

Parameters

date

a GDate to get the month from

Passed as self

get-sunday-week-of-year

(define-values (%return) (date:get-sunday-week-of-year self))

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.

Parameters

date

a GDate

Passed as self

get-weekday

(define-values (%return) (date:get-weekday self))

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

Parameters

date

a GDate

Passed as self

get-year

(define-values (%return) (date:get-year self))

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

Parameters

date

a GDate

Passed as self

is-first-of-month?

(define-values (%return) (date:is-first-of-month? self))

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

Parameters

date

a GDate to check

Passed as self

is-last-of-month?

(define-values (%return) (date:is-last-of-month? self))

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

Parameters

date

a GDate to check

Passed as self

order

(define-values () (date:order self date2))

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

Parameters

date1

the first date

Passed as self

date2

the second date

Passed as date2

set-day

(define-values () (date:set-day self day))

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

Parameters

date

a GDate

Passed as self

day

day to set

Passed as day

set-dmy

(define-values () (date:set-dmy self day month y))

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.

Parameters

date

a GDate

Passed as self

day

day

Passed as day

month

month

Passed as month

y

year

Passed as y

set-julian

(define-values () (date:set-julian self julian-date))

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

Parameters

date

a GDate

Passed as self

julian_date

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

Passed as julian-date

set-month

(define-values () (date:set-month self month))

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

Parameters

date

a GDate

Passed as self

month

month to set

Passed as month

set-parse

(define-values () (date:set-parse self str))

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 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).

Parameters

date

a GDate to fill in

Passed as self

str

string to parse

Passed as str

set-time

(define-values () (date:set-time self time-))

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

Parameters

date

a GDate.

Passed as self

time_

GTime value to set.

Passed as time-

set-time-t

(define-values () (date:set-time-t self timet))

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);

Parameters

date

a GDate

Passed as self

timet

time_t value to set

Passed as timet

set-year

(define-values () (date:set-year self year))

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

Parameters

date

a GDate

Passed as self

year

year to set

Passed as year

subtract-days

(define-values () (date:subtract-days self n-days))

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

date

a GDate to decrement

Passed as self

n_days

number of days to move

Passed as n-days

subtract-months

(define-values () (date:subtract-months self n-months))

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

date

a GDate to decrement

Passed as self

n_months

number of months to move

Passed as n-months

subtract-years

(define-values () (date:subtract-years self n-years))

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

date

a GDate to decrement

Passed as self

n_years

number of years to move

Passed as n-years

to-struct-tm

(define-values () (date:to-struct-tm self tm))

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

date

a GDate to set the struct tm from

Passed as self

tm

struct tm to fill

Passed as tm

valid?

(define-values (%return) (date:valid? self))

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.

Parameters

date

a GDate to check

Passed as self

date:new-julian

(define-values (%return) (date:new-julian julian-day))

Undocumented

Parameters

julian_day

Passed as julian-day

date:new-dmy

(define-values (%return) (date:new-dmy day month year))

Undocumented

Parameters

day

Passed as day

month

Passed as month

year

Passed as year

date:new

(define-values (%return) (date:new))

Undocumented

date:get-days-in-month

(define-values (%return) (date:get-days-in-month month year))

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

Parameters

month

month

Passed as month

year

year

Passed as year

date:get-monday-weeks-in-year

(define-values (%return) (date:get-monday-weeks-in-year 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.)

Parameters

year

a year

Passed as year

date:get-sunday-weeks-in-year

(define-values (%return) (date:get-sunday-weeks-in-year year))

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

Passed as year

date:is-leap-year?

(define-values (%return) (date:is-leap-year? year))

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

Passed as year

date:strftime

(define-values (%return) (date:strftime s slen format date))

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 g_date_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

Passed as s

slen

buffer size

Passed as slen

format

format string

Passed as format

date

valid GDate

Passed as date

date:valid-day?

(define-values (%return) (date:valid-day? day))

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

Passed as day

date:valid-dmy?

(define-values (%return) (date:valid-dmy? day month year))

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).

Parameters

day

day

Passed as day

month

month

Passed as month

year

year

Passed as year

date:valid-julian?

(define-values (%return) (date:valid-julian? julian-date))

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

Passed as julian-date

date:valid-month?

(define-values (%return) (date:valid-month? month))

Returns TRUE if the month value is valid. The 12 GDateMonth enumeration values are the only valid months.

Parameters

month

month

Passed as month

date:valid-weekday?

(define-values (%return) (date:valid-weekday? weekday))

Returns TRUE if the weekday is valid. The seven GDateWeekday enumeration values are the only valid weekdays.

Parameters

weekday

weekday

Passed as weekday

date:valid-year?

(define-values (%return) (date:valid-year? year))

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.

Parameters

year

year

Passed as year