tm(3type)                                                            tm(3type)

NAME
       tm - broken-down time

LIBRARY
       Standard C library (libc)

SYNOPSIS
       #include <time.h>

       struct tm {
           int         tm_sec;    /* Seconds          [0, 60] */
           int         tm_min;    /* Minutes          [0, 59] */
           int         tm_hour;   /* Hour             [0, 23] */
           int         tm_mday;   /* Day of the month [1, 31] */
           int         tm_mon;    /* Month            [0, 11]  (January = 0) */
           int         tm_year;   /* Year minus 1900 */
           int         tm_wday;   /* Day of the week  [0, 6]   (Sunday = 0) */
           int         tm_yday;   /* Day of the year  [0, 365] (Jan/01 = 0) */
           int         tm_isdst;  /* Daylight savings flag */

           long        tm_gmtoff; /* Seconds East of UTC */
           const char *tm_zone;   /* Timezone abbreviation */
       };

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       tm_gmtoff, tm_zone:
           Since glibc 2.20:
               _DEFAULT_SOURCE
           glibc 2.20 and earlier:
               _BSD_SOURCE

DESCRIPTION
       Describes time, broken down into distinct components.

       tm_isdst describes whether daylight saving time is in effect at the
       time described.  The value is positive if daylight saving time is in
       effect, zero if it is not, and negative if the information is not
       available.

       tm_gmtoff is the difference, in seconds, of the timezone represented by
       this broken-down time and UTC (this is the additive inverse of
       timezone(3)).

       tm_zone is the equivalent of tzname(3) for the timezone represented by
       this broken-down time.

VERSIONS
       In C90, tm_sec could represent values in the range [0, 61], which could
       represent a double leap second.  UTC doesn't permit double leap
       seconds, so it was limited to 60 in C99.

       timezone(3), as a variable, is an XSI extension: some systems provide
       the V7-compatible timezone(3) function.  The tm_gmtoff field provides
       an alternative (with the opposite sign) for those systems.

       tm_zone points to static storage and may be overridden on subsequent
       calls to localtime(3) and similar functions (however, this never
       happens under glibc).

STANDARDS
       C11, POSIX.1-2008.

HISTORY
       C89, POSIX.1-2001.

       tm_gmtoff and tm_zone originate from 4.3BSD-Tahoe (where tm_zone is a
       char *).

NOTES
       tm_sec can represent a leap second with the value 60.

SEE ALSO
       ctime(3), strftime(3), strptime(3), time(7)

Linux man-pages 6.8               2024-05-02                         tm(3type)