mktime(3)                                                     mktime(3)

  mktime()

  NAME

    mktime() - transform format of time value

  SYNOPSIS

    #include 

    time_t mktime (struct tm *tm)

  DESCRIPTION

    The function mktime(3) converts the local time, expressed in the structure
    pointed to by tm into a time_t time value with the same encoding as that
    of the values returned by the time(2) function, that is, seconds from the
    Epoch, UTC.

    The original values of the tm_wday and tm_yday components of the structure
    are ignored, and the original values of the other components are not
    restricted to their normal ranges. (A positive or zero value for tm_isdst
    causes mktime(3) to presume initially that summer time (for example,
    Daylight Saving Time) is or is not in effect for the specified time,
    respectively. A negative value for tm_isdst causes the mktime(3) function
    to attempt to divine whether summer time is in effect for the specified
    time.)

    On successful completion, the values of the tm_wday and tm_yday components
    of the structure are set appropriately, and the other components are set
    to represent the specified calendar time, but with their values forced to
    their normal ranges; the final value of tm_mday is not set until tm_mon
    and tm_year are determined. Mktime(3) returns the specified calendar time;
    if the calendar time cannot be represented, it returns -1.

    External declarations as well as the tm structure definition are in the
     include file. The tm structure includes at least the following
    fields:
    int     tm_sec;       seconds (0 - 60)

    int     tm_min;       minutes (0 - 59)

    int     tm_hour;      hours (0 - 23)

    int     tm_mday;      day of month (1 - 31)

    int     tm_mon;       month of year (0 - 11)

    int     tm_year;      year - 1900

    int     tm_wday;      day of week (Sunday = 0)

    int     tm_yday;      day of year (0 - 365)

    int     tm_isdst;     is summer time in effect?

    The field tm_isdst is non-zero if summer time is in effect.

  SEE ALSO

    date(1)

    asctime(3)

    ctime(3)

    gmtime(3)

    localtime(3)

    difftime(3)

    getenv(3)

    time(2)

    tzset(3)

  USAGE NOTES

    The mktime function is not thread safe.

    The mktime function is not async-signal safe.