g_get_current_time ()

void
g_get_current_time (GTimeVal *result);

Equivalent to the UNIX gettimeofday() function, but portable.

You may find g_get_real_time() to be more convenient.

g_usleep ()

void
g_usleep (gulong microseconds);

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.

g_time_val_add ()

void
g_time_val_add (GTimeVal *time_,
                glong microseconds);

Adds the given number of microseconds to time_ . microseconds can also be negative to decrease the value of time_ .

g_time_val_from_iso8601 ()

gboolean
g_time_val_from_iso8601 (const gchar *iso_date,
                         GTimeVal *time_);

Converts a string containing an ISO 8601 encoded date and time to a GTimeVal and puts it into time_ .

iso_date must include year, month, day, hours, minutes, and seconds. It can optionally include fractions of a second and a time zone indicator. (In the absence of any time zone indication, the timestamp is assumed to be in local time.)

Since: 2.12

g_time_val_to_iso8601 ()

gchar *
g_time_val_to_iso8601 (GTimeVal *time_);

Converts time_ into an RFC 3339 encoded string, relative to the Coordinated Universal Time (UTC). This is one of the many formats allowed by ISO 8601.

ISO 8601 allows a large number of date/time formats, with or without punctuation and optional elements. The format returned by this function is a complete date and time, with optional punctuation included, the UTC time zone represented as "Z", and the tv_usec part included if and only if it is nonzero, i.e. either "YYYY-MM-DDTHH:MM:SSZ" or "YYYY-MM-DDTHH:MM:SS.fffffZ".

This corresponds to the Internet date/time format defined by RFC 3339, and to either of the two most-precise formats defined by the W3C Note Date and Time Formats. Both of these documents are profiles of ISO 8601.

Use g_date_time_format() or g_strdup_printf() if a different variation of ISO 8601 format is required.

If time_ represents a date which is too large to fit into a struct tm, NULL will be returned. This is platform dependent, but it is safe to assume years up to 3000 are supported. The return value of g_time_val_to_iso8601() has been nullable since GLib 2.54; before then, GLib would crash under the same conditions.

Since: 2.12

g_get_monotonic_time ()

gint64
g_get_monotonic_time (void);

Queries the system monotonic time.

The monotonic clock will always increase and doesn't suffer discontinuities when the user (or NTP) changes the system time. It may or may not continue to tick during times where the machine is suspended.

We try to use the clock that corresponds as closely as possible to the passage of time as measured by system calls such as poll() but it may not always be possible to do this.

Since: 2.28

g_get_real_time ()

gint64
g_get_real_time (void);

Queries the system wall-clock time.

This call is functionally equivalent to g_get_current_time() except that the return value is often more convenient than dealing with a GTimeVal.

You should only use this call if you are actually interested in the real wall-clock time. g_get_monotonic_time() is probably more useful for measuring intervals.

Since: 2.28

g_date_new ()

GDate *
g_date_new (void);

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().

g_date_new_dmy ()

GDate *
g_date_new_dmy (GDateDay day,
                GDateMonth month,
                GDateYear year);

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.

g_date_new_julian ()

GDate *
g_date_new_julian (guint32 julian_day);

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.

g_date_clear ()

void
g_date_clear (GDate *date,
              guint n_dates);

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().

g_date_free ()

void
g_date_free (GDate *date);

Frees a GDate returned from g_date_new().

g_date_set_day ()

void
g_date_set_day (GDate *date,
                GDateDay day);

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

g_date_set_month ()

void
g_date_set_month (GDate *date,
                  GDateMonth month);

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

g_date_set_year ()

void
g_date_set_year (GDate *date,
                 GDateYear year);

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

g_date_set_dmy ()

void
g_date_set_dmy (GDate *date,
                GDateDay day,
                GDateMonth month,
                GDateYear 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.

g_date_set_julian ()

void
g_date_set_julian (GDate *date,
                   guint32 julian_date);

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

g_date_set_time ()

void
g_date_set_time (GDate *date,
                 GTime time_);

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

g_date_set_time_t ()

void
g_date_set_time_t (GDate *date,
                   time_t 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:

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g_date_set_time_t (date, time (NULL));

Since: 2.10

g_date_set_time_val ()

void
g_date_set_time_val (GDate *date,
                     GTimeVal *timeval);

Sets the value of a date from a GTimeVal value. Note that the tv_usec member is ignored, because GDate can't make use of the additional precision.

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

Since: 2.10

g_date_set_parse ()

void
g_date_set_parse (GDate *date,
                  const gchar *str);

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).

g_date_add_days ()

void
g_date_add_days (GDate *date,
                 guint n_days);

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

g_date_subtract_days ()

void
g_date_subtract_days (GDate *date,
                      guint 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.

g_date_add_months ()

void
g_date_add_months (GDate *date,
                   guint 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.

g_date_subtract_months ()

void
g_date_subtract_months (GDate *date,
                        guint 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.

g_date_add_years ()

void
g_date_add_years (GDate *date,
                  guint 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.

g_date_subtract_years ()

void
g_date_subtract_years (GDate *date,
                       guint 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.

g_date_days_between ()

gint
g_date_days_between (const GDate *date1,
                     const GDate *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.

g_date_compare ()

gint
g_date_compare (const GDate *lhs,
                const GDate *rhs);

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

g_date_clamp ()

void
g_date_clamp (GDate *date,
              const GDate *min_date,
              const GDate *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.

g_date_order ()

void
g_date_order (GDate *date1,
              GDate *date2);

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

g_date_get_day ()

GDateDay
g_date_get_day (const GDate *date);

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

g_date_get_month ()

GDateMonth
g_date_get_month (const GDate *date);

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

g_date_get_year ()

GDateYear
g_date_get_year (const GDate *date);

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

g_date_get_julian ()

guint32
g_date_get_julian (const GDate *date);

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.

g_date_get_weekday ()

GDateWeekday
g_date_get_weekday (const GDate *date);

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

g_date_get_day_of_year ()

guint
g_date_get_day_of_year (const GDate *date);

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

g_date_get_days_in_month ()

guint8
g_date_get_days_in_month (GDateMonth month,
                          GDateYear year);

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

g_date_is_first_of_month ()

gboolean
g_date_is_first_of_month (const GDate *date);

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

g_date_is_last_of_month ()

gboolean
g_date_is_last_of_month (const GDate *date);

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

g_date_is_leap_year ()

gboolean
g_date_is_leap_year (GDateYear 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.

g_date_get_monday_week_of_year ()

guint
g_date_get_monday_week_of_year (const GDate *date);

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.

g_date_get_monday_weeks_in_year ()

guint8
g_date_get_monday_weeks_in_year (GDateYear 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.)

g_date_get_sunday_week_of_year ()

guint
g_date_get_sunday_week_of_year (const GDate *date);

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.

g_date_get_sunday_weeks_in_year ()

guint8
g_date_get_sunday_weeks_in_year (GDateYear 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.)

g_date_get_iso8601_week_of_year ()

guint
g_date_get_iso8601_week_of_year (const GDate *date);

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

Since: 2.6

g_date_strftime ()

gsize
g_date_strftime (gchar *s,
                 gsize slen,
                 const gchar *format,
                 const GDate *date);

Generates a printed representation of the date, in a locale-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.

g_date_to_struct_tm ()

void
g_date_to_struct_tm (const GDate *date,
                     struct tm *tm);

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

g_date_valid ()

gboolean
g_date_valid (const GDate *date);

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.

g_date_valid_day ()

gboolean
g_date_valid_day (GDateDay day);

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

g_date_valid_month ()

gboolean
g_date_valid_month (GDateMonth month);

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

g_date_valid_year ()

gboolean
g_date_valid_year (GDateYear 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.

g_date_valid_dmy ()

gboolean
g_date_valid_dmy (GDateDay day,
                  GDateMonth month,
                  GDateYear 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).

g_date_valid_julian ()

gboolean
g_date_valid_julian (guint32 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.

g_date_valid_weekday ()

gboolean
g_date_valid_weekday (GDateWeekday weekday);

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

G_USEC_PER_SEC

#define G_USEC_PER_SEC 1000000

Number of microseconds in one second (1 million). This macro is provided for code readability.

struct GTimeVal

struct GTimeVal {
  glong tv_sec;
  glong tv_usec;
};

Represents a precise time, with seconds and microseconds. Similar to the struct timeval returned by the gettimeofday() UNIX system call.

GLib is attempting to unify around the use of 64bit integers to represent microsecond-precision time. As such, this type will be removed from a future version of GLib.

struct GDate

struct GDate {
  guint julian_days : 32; /* julian days representation - we use a
                           *  bitfield hoping that 64 bit platforms
                           *  will pack this whole struct in one big
                           *  int
                           */

  guint julian : 1;    /* julian is valid */
  guint dmy    : 1;    /* dmy is valid */

  /* DMY representation */
  guint day    : 6;
  guint month  : 4;
  guint year   : 16;
};

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.

GTime

typedef gint32  GTime;

Simply a replacement for time_t. It has been deprecated since it is not equivalent to time_t on 64-bit platforms with a 64-bit time_t. Unrelated to GTimer.

Note that GTime is defined to always be a 32-bit integer, unlike time_t which may be 64-bit on some systems. Therefore, GTime will overflow in the year 2038, and you cannot use the address of a GTime variable as argument to the UNIX time() function.

Instead, do the following:

1
2
3
4
5

time_t ttime;
GTime gtime;

time (&ttime);
gtime = (GTime)ttime;

enum GDateDMY

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.

GDateDay

typedef guint8  GDateDay;   /* day of the month */

Integer representing a day of the month; between 1 and 31. G_DATE_BAD_DAY represents an invalid day of the month.

enum GDateMonth

Enumeration representing a month; values are G_DATE_JANUARY, G_DATE_FEBRUARY, etc. G_DATE_BAD_MONTH is the invalid value.

GDateYear

typedef guint16 GDateYear;

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.

enum GDateWeekday

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_DAY

#define G_DATE_BAD_DAY    0U

Represents an invalid GDateDay.

G_DATE_BAD_JULIAN

#define G_DATE_BAD_JULIAN 0U

Represents an invalid Julian day number.

G_DATE_BAD_YEAR

#define G_DATE_BAD_YEAR   0U

Represents an invalid year.