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    CTIME(3)            Linux Programmer's Manual            CTIME(3)

    NAME
           asctime,  ctime,  gmtime,  localtime,  mktime  - transform
           binary date and time to ASCII

    SYNOPSIS
           #include <time.h>

           char *asctime(const struct tm *timeptr);

           char *ctime(const time_t *timep);

           struct tm *gmtime(const time_t *timep);

           struct tm *localtime(const time_t *timep);

           time_t mktime(struct tm *timeptr);

           extern char *tzname[2];
           long int timezone;
           extern int daylight;

    DESCRIPTION
           The ctime(), gmtime() and localtime() functions  all  take
           an  argument of data type time_t which represents calendar
           time.  When interpreted as an absolute time value, it rep-
           resents  the  number  of seconds elapsed since 00:00:00 on
           January 1, 1970, Coordinated Universal Time (UTC).

           The asctime() and mktime() functions both take an argument
           representing  broken-down time which is a binary represen-
           tation separated into year, month, day, etc.   Broken-down
           time  is  stored  in  the structure tm which is defined in
           <time.h> as follows:

                  struct tm
                  {
                          int     tm_sec;         /* seconds */
                          int     tm_min;         /* minutes */
                          int     tm_hour;        /* hours */
                          int     tm_mday;        /* day of the month */
                          int     tm_mon;         /* month */
                          int     tm_year;        /* year */
                          int     tm_wday;        /* day of the week */
                          int     tm_yday;        /* day in the year */
                          int     tm_isdst;       /* daylight saving time */
                  };

           The members of the tm structure are:

           tm_sec The number of seconds after the minute, normally in
                  the range 0 to 59, but can be up to 61 to allow for
                  leap seconds.

           tm_min The number of minutes after the hour, in the  range

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                  0 to 59.

           tm_hour
                  The  number  of hours past midnight, in the range 0
                  to 23.

           tm_mday
                  The day of the month, in the range 1 to 31.

           tm_mon The number of months since January, in the range  0
                  to 11.

           tm_year
                  The number of years since 1900.

           tm_wday
                  The  number of days since Sunday, in the range 0 to
                  6.

           tm_yday
                  The number of days since January 1, in the range  0
                  to 365.

           tm_isdst
                  A  flag that indicates 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.

           The ctime() function converts the calendar time timep into
           a string of the form

                  "Wed Jun 30 21:49:08 1993\n"

           The abbreviations for the days  of  the  week  are  `Sun',
           `Mon',  `Tue', `Wed', `Thu', `Fri', and `Sat'.  The abbre-
           viations for the months are `Jan',  `Feb',  `Mar',  `Apr',
           `May',  `Jun',  `Jul',  `Aug',  `Sep',  `Oct',  `Nov', and
           `Dec'.  The return value points to a statically  allocated
           string  which  might be overwritten by subsequent calls to
           any of the date and time  functions.   The  function  also
           sets  the  external variable tzname with information about
           the current time zone.

           The gmtime() function converts the calendar time timep  to
           broken-down  time representation, expressed in Coordinated
           Universal Time (UTC).

           The localtime() function converts the calendar time  timep
           to  broken-time  representation, expressed relative to the
           user's specified  time  zone.     The  function  sets  the
           external  variables tzname with information about the cur-
           rent time  zone,  timezone  with  the  difference  between

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    CTIME(3)            Linux Programmer's Manual            CTIME(3)

           Coordinated  Universal  Time (UTC) and local standard time
           in seconds, and daylight to a non-zero value  if  standard
           US daylight savings time rules apply.

           The asctime() function converts the broken-down time value
           timeptr into a string with the  same  format  as  ctime().
           The  return  value points to a statically allocated string
           which might be overwritten by subsequent calls to  any  of
           the date and time functions.

           The  mktime()  function converts a broken-down time struc-
           ture  to  calendar  time  representation.   The   function
           ignores  the  specified  contents of the structure members
           tm_wday and tm_yday and recomputes  them  from  the  other
           information  in  the  broken-down time structure.  Calling
           mktime() also  sets  the  external  variable  tzname  with
           information about the current time zone.  If the specified
           broken-down time cannot be represented as  calendar  time,
           mktime()  returns  a  value  of  (time_t)(-1) and does not
           alter the tm_wday and tm_yday members of  the  broken-down
           time structure.

    CONFORMING TO
           SVID 3, POSIX, BSD 4.3, ISO 9899

### SEE ALSO

date, gettimeofday, time, tzset, difftime, strftime,

###

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