## e-cal-time-util

e-cal-time-util — Time management utility functions.

## Synopsis

    int                 time_days_in_month                  (int year,
                                                             int month);
    int                 time_day_of_year                    (int day,
                                                             int month,
                                                             int year);
    int                 time_day_of_week                    (int day,
                                                             int month,
                                                             int year);
    gboolean            time_is_leap_year                   (int year);
    int                 time_leap_years_up_to               (int year);
    char*               isodate_from_time_t                 (time_t t);
    time_t              time_from_isodate                   (const char *str);
    time_t              time_add_day                        (time_t time,
                                                             int days);
    time_t              time_add_week                       (time_t time,
                                                             int weeks);
    time_t              time_day_begin                      (time_t t);
    time_t              time_day_end                        (time_t t);
    time_t              time_add_day_with_zone              (time_t time,
                                                             int days,
                                                             icaltimezone *zone);
    time_t              time_add_week_with_zone             (time_t time,
                                                             int weeks,
                                                             icaltimezone *zone);
    time_t              time_add_month_with_zone            (time_t time,
                                                             int months,
                                                             icaltimezone *zone);
    time_t              time_year_begin_with_zone           (time_t time,
                                                             icaltimezone *zone);
    time_t              time_month_begin_with_zone          (time_t time,
                                                             icaltimezone *zone);
    time_t              time_week_begin_with_zone           (time_t time,
                                                             int week_start_day,
                                                             icaltimezone *zone);
    time_t              time_day_begin_with_zone            (time_t time,
                                                             icaltimezone *zone);
    time_t              time_day_end_with_zone              (time_t time,
                                                             icaltimezone *zone);
    void                time_to_gdate_with_zone             (GDate *date,
                                                             time_t time,
                                                             icaltimezone *zone);
    struct tm           icaltimetype_to_tm                  (struct icaltimetype *itt);
    struct tm           icaltimetype_to_tm_with_zone        (struct icaltimetype *itt,
                                                             icaltimezone *from_zone,
                                                             icaltimezone *to_zone);
    struct icaltimetype tm_to_icaltimetype                  (struct tm *tm,
                                                             gboolean is_date);

## Description

## Details

### time_days_in_month ()

    int                 time_days_in_month                  (int year,
                                                             int month);

Returns the number of days in the month. Year is the normal year, e.g. 2001. Month is 0 (Jan) to 11 (Dec).

`year` : | The year.
`month` : | The month.
Returns : | number of days in the given month/year.

### time_day_of_year ()

    int                 time_day_of_year                    (int day,
                                                             int month,
                                                             int year);

Returns the 1-based day number within the year of the specified date. Year is the normal year, e.g. 2001. Month is 0 to 11.

`day` : | The day.
`month` : | The month.
`year` : | The year.
Returns : | the day of the year.

### time_day_of_week ()

    int                 time_day_of_week                    (int day,
                                                             int month,
                                                             int year);

Returns the day of the week for the specified date, 0 (Sun) to 6 (Sat). For the days that were removed on the Gregorian reformation, it returns Thursday. Year is the normal year, e.g. 2001. Month is 0 to 11.

`day` : | The day.
`month` : | The month.
`year` : | The year.
Returns : | the day of the week for the given date.

### time_is_leap_year ()

    gboolean            time_is_leap_year                   (int year);

Returns whether the specified year is a leap year. Year is the normal year, e.g. 2001.

`year` : | The year.
Returns : | TRUE if the year is leap, FALSE if not.

### time_leap_years_up_to ()

    int                 time_leap_years_up_to               (int year);

Returns the number of leap years since year 1 up to (but not including) the specified year. Year is the normal year, e.g. 2001.

`year` : | The year.
Returns : | number of leap years.

### isodate_from_time_t ()

    char*               isodate_from_time_t                 (time_t t);

Creates an ISO 8601 UTC representation from a time value.

`t` : | A time value.
Returns : | String with the ISO 8601 representation of the UTC time.

### time_from_isodate ()

    time_t              time_from_isodate                   (const char *str);

Converts an ISO 8601 UTC time string into a time_t value.

`str` : | Date/time value in ISO 8601 format.
Returns : | Time_t corresponding to the specified ISO string. Note that we only allow UTC times at present.

### time_add_day ()

    time_t              time_add_day                        (time_t time,
                                                             int days);

Adds a day onto the time, using local time. Note that if clocks go forward due to daylight savings time, there are some non-existent local times, so the hour may be changed to make it a valid time. This also means that it may not be wise to keep calling `time_add_day()` to step through a certain period - if the hour gets changed to make it valid time, any further calls to `time_add_day()` will also return this hour, which may not be what you want.

`time` : | A time_t value.
`days` : | Number of days to add.
Returns : | a time_t value containing `time` plus the days added.

### time_add_week ()

    time_t              time_add_week                       (time_t time,
                                                             int weeks);

Adds the given number of weeks to a time value.

`time` : | A time_t value.
`weeks` : | Number of weeks to add.
Returns : | a time_t value containing `time` plus the weeks added.

### time_day_begin ()

    time_t              time_day_begin                      (time_t t);

Returns the start of the day, according to the local time.

`t` : | A time_t value.
Returns : | the time corresponding to the beginning of the day.

### time_day_end ()

    time_t              time_day_end                        (time_t t);

Returns the end of the day, according to the local time.

`t` : | A time_t value.
Returns : | the time corresponding to the end of the day.

### time_add_day_with_zone ()

    time_t              time_add_day_with_zone              (time_t time,
                                                             int days,
                                                             icaltimezone *zone);

Adds or subtracts a number of days to/from the given time_t value, using the given timezone. NOTE: this function is only here to make the transition to the timezone functions easier. New code should use icaltimetype values and `icaltime_adjust()` to add or subtract days, hours, minutes & seconds.

`time` : | A time_t value.
`days` : | Number of days to add.
`zone` : | Timezone to use.
Returns : | a time_t value containing `time` plus the days added.

### time_add_week_with_zone ()

    time_t              time_add_week_with_zone             (time_t time,
                                                             int weeks,
                                                             icaltimezone *zone);

Adds or subtracts a number of weeks to/from the given time_t value, using the given timezone. NOTE: this function is only here to make the transition to the timezone functions easier. New code should use icaltimetype values and `icaltime_adjust()` to add or subtract days, hours, minutes & seconds.

`time` : | A time_t value.
`weeks` : | Number of weeks to add.
`zone` : | Timezone to use.
Returns : | a time_t value containing `time` plus the weeks added.

### time_add_month_with_zone ()

    time_t              time_add_month_with_zone            (time_t time,
                                                             int months,
                                                             icaltimezone *zone);

Adds or subtracts a number of months to/from the given time_t value, using the given timezone.

If the day would be off the end of the month (e.g. adding 1 month to 30th January, would lead to an invalid day, 30th February), it moves it down to the last day in the month, e.g. 28th Feb (or 29th in a leap year.)

NOTE: this function is only here to make the transition to the timezone functions easier. New code should use icaltimetype values and `icaltime_adjust()` to add or subtract days, hours, minutes & seconds.

`time` : | A time_t value.
`months` : | Number of months to add.
`zone` : | Timezone to use.
Returns : | a time_t value containing `time` plus the months added.

### time_year_begin_with_zone ()

    time_t              time_year_begin_with_zone           (time_t time,
                                                             icaltimezone *zone);

Returns the start of the year containing the given time_t, using the given timezone. NOTE: this function is only here to make the transition to the timezone functions easier. New code should use icaltimetype values and `icaltime_adjust()` to add or subtract days, hours, minutes & seconds.

`time` : | A time_t value.
`zone` : | Timezone to use.
Returns : | the beginning of the year.

### time_month_begin_with_zone ()

    time_t              time_month_begin_with_zone          (time_t time,
                                                             icaltimezone *zone);

Returns the start of the month containing the given time_t, using the given timezone. NOTE: this function is only here to make the transition to the timezone functions easier. New code should use icaltimetype values and `icaltime_adjust()` to add or subtract days, hours, minutes & seconds.

`time` : | A time_t value.
`zone` : | Timezone to use.
Returns : | the beginning of the month.

### time_week_begin_with_zone ()

    time_t              time_week_begin_with_zone           (time_t time,
                                                             int week_start_day,
                                                             icaltimezone *zone);

Returns the start of the week containing the given time_t, using the given timezone. week_start_day should use the same values as `mktime()`, i.e. 0 (Sun) to 6 (Sat). NOTE: this function is only here to make the transition to the timezone functions easier. New code should use icaltimetype values and `icaltime_adjust()` to add or subtract days, hours, minutes & seconds.

`time` : | A time_t value.
`week_start_day` : | Day to use as the starting of the week.
`zone` : | Timezone to use.
Returns : | the beginning of the week.

### time_day_begin_with_zone ()

    time_t              time_day_begin_with_zone            (time_t time,
                                                             icaltimezone *zone);

Returns the start of the day containing the given time_t, using the given timezone. NOTE: this function is only here to make the transition to the timezone functions easier. New code should use icaltimetype values and `icaltime_adjust()` to add or subtract days, hours, minutes & seconds.

`time` : | A time_t value.
`zone` : | Timezone to use.
Returns : | the beginning of the day.

### time_day_end_with_zone ()

    time_t              time_day_end_with_zone              (time_t time,
                                                             icaltimezone *zone);

Returns the end of the day containing the given time_t, using the given timezone. (The end of the day is the start of the next day.) NOTE: this function is only here to make the transition to the timezone functions easier. New code should use icaltimetype values and `icaltime_adjust()` to add or subtract days, hours, minutes & seconds.

`time` : | A time_t value.
`zone` : | Timezone to use.
Returns : | the end of the day.

### time_to_gdate_with_zone ()

    void                time_to_gdate_with_zone             (GDate *date,
                                                             time_t time,
                                                             icaltimezone *zone);

Converts a time_t value to a GDate structure using the specified timezone. This is analogous to `g_date_set_time()` but takes the timezone into account.

`date` : | Destination GDate value.
`time` : | A time value.
`zone` : | Desired timezone for destination `date`, or NULL if the UTC timezone is desired.

### icaltimetype_to_tm ()

    struct tm           icaltimetype_to_tm                  (struct icaltimetype *itt);

Convers an icaltimetype structure into a GLibc's struct tm.

`itt` : | An icaltimetype structure.
Returns : | The converted time as a struct tm. All fields will be set properly except for tm.tm_yday.

### icaltimetype_to_tm_with_zone ()

    struct tm           icaltimetype_to_tm_with_zone        (struct icaltimetype *itt,
                                                             icaltimezone *from_zone,
                                                             icaltimezone *to_zone);

Converts a time value from one timezone to another, and returns a struct tm representation of the time.

`itt` : | A time value.
`from_zone` : | Source timezone.
`to_zone` : | Destination timezone.
Returns : | The converted time as a struct tm. All fields will be set properly except for tm.tm_yday.

### tm_to_icaltimetype ()

    struct icaltimetype tm_to_icaltimetype                  (struct tm *tm,
                                                             gboolean is_date);

Converts a struct tm into an icaltimetype.

`tm` : | A struct tm.
`is_date` : | Whether the given time is a date only or not.
Returns : | The converted time as an icaltimetype.