tm.h

Utility library for struct tm.

TM_WDAY_SUN

Sunday in struct tm::tm_wday. 

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TM_WDAY_MON

Monday in struct tm::tm_wday. 

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(1)
TM_WDAY_TUE

Tuesday in struct tm::tm_wday. 

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TM_WDAY_WED

Wednesday in struct tm::tm_wday. 

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TM_WDAY_THU

Thursday in struct tm::tm_wday. 

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TM_WDAY_FRI

Friday in struct tm::tm_wday. 

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TM_WDAY_SAT

Saturday in struct tm::tm_wday. 

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TM_MON_JAN

January in struct tm::tm_mon 

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TM_MON_FEB

February in struct tm::tm_mon 

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TM_MON_MAR

March in struct tm::tm_mon 

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TM_MON_APR

April in struct tm::tm_mon 

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TM_MON_MAY

May in struct tm::tm_mon 

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TM_MON_JUN

June in struct tm::tm_mon 

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TM_MON_JUL

July in struct tm::tm_mon 

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TM_MON_AUG

August in struct tm::tm_mon 

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TM_MON_SEP

September in struct tm::tm_mon 

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TM_MON_OCT

October in struct tm::tm_mon 

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TM_MON_NOV

November in struct tm::tm_mon 

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(10)
TM_MON_DEC

December in struct tm::tm_mon 

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(11)
const int8_t TM_MON_DAYS()

The number of days in common years.

See also

http://oeis.org/A008685

const int16_t TM_MON_DAYS_ACCU()

The prefixsum of the number of days in common years.

See also

http://oeis.org/A061251

int tm_is_leap_year(unsigned year)

Tells if a given year is a leap year in the Gregorian calendar.

Parameters

year:The year. Probably should be ≥ 1582, but needs to be ≥ 1.

Return values

  • 1 if it is a leap year, 0 if it is a common year.
int tm_doomsday(int year)

Returns the congruent weekday of the Doomsday (March 0).

Only applies for years in the Gregorian calendar.

Parameters

year:The year. Probably should be ≥ 1582, but needs to be ≥ 1.

Return values

  • The result % 7 is the weekday of the Doomsday of the given year.
void tm_get_wyday(int year, int mon, int mday, int * wday, int * yday)

Calculates the day of the year and the weekday of a given date.

Illegal dates are not catched.

Parameters

year:The year. Probably should be ≥ 1582, but needs to be ≥ 1.
mon:The month, TM_MON_JAN to TM_MON_DEC.
mday:The day in the month, 1 to 31.
wday:Returns the day of the week.
yday:Returns the day of the year (Jan 1st is 0).

void tm_fill_derived_values(struct tm * tm)

Fills in struct tm::tm_wday and struct tm::tm_yday given a date.

struct tm::tm_year, struct tm::tm_mon, and struct tm::tm_mday need to be set before you call this function.

Parameters

tm:The datum to operate on.

int tm_is_valid_date(int year, int mon, int mday)

Tests if a date is valid.

Dates before 1582-10-15 are invalid.

Parameters

year:The year.
mon:The month.
mday:The day in the month.

Return values

  • 0 iff the date is invalid.
int tm_is_valid_time(int hour, int min, int sec)

Shallow test if a time is valid.

This function accepts leap seconds at any given time, because the timezone is unknown.

Parameters

hour:The hour.
min:The minutes.
sec:The seconds.

Return values

  • 0 iff the time is invalid.