newctime

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NAME

       asctime, ctime, difftime, gmtime, localtime, mktime - con-
       vert date and time to ASCII


SYNOPSIS

       extern char *tzname[2];

       void tzset()

       #include <sys/types.h>

       char *ctime(clock)
       const time_t *clock;

       double difftime(time1, time0)
       time_t time1;
       time_t time0;

       #include <time.h>

       char *asctime(tm)
       const struct tm *tm;

       struct tm *localtime(clock)
       const time_t *clock;

       struct tm *gmtime(clock)
       const time_t *clock;

       time_t mktime(tm)
       struct tm *tm;

       cc ... -lz


DESCRIPTION

       Ctime converts a long integer, pointed to by clock, repre-
       senting the time in seconds since 00:00:00 UTC, January 1,
       1970, and returns a pointer to a  26-character  string  of
       the form
                      Thu Nov 24 18:22:48 1986\n\0
       All the fields have constant width.

       Localtime and gmtime return pointers to ``tm'' structures,
       described below.  Localtime corrects for the time zone and
       any time zone adjustments (such as Daylight Saving Time in
       the U.S.A.).  Before doing so, localtime calls  tzset  (if
       tzset  has not been called in the current process).  After
       filling  in  the  ``tm''  structure,  localtime  sets  the
       tm_isdst'th  element  of  tzname  to a pointer to an ASCII
       string that's the time zone abbreviation to be  used  with
       localtime's return value.

       Gmtime converts to Coordinated Universal Time.

       Asctime converts a time value contained in a ``tm'' struc-
       ture to a 26-character string, as shown in the above exam-
       ple, and returns a pointer to the string.

       Mktime  converts  the broken-down time, expressed as local
       time, in the structure pointed to by tm  into  a  calendar
       time  value  with  the same encoding as that of the values
       returned by the time function.  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 to presume initially
       that summer time (for example, Daylight Saving Time in the
       U.S.A.)  respectively, is or is  not  in  effect  for  the
       specified  time.  A negative value for tm_isdst causes the
       mktime function to attempt to divine whether  summer  time
       is  in effect for the specified time.)  On successful com-
       pletion, the values of the tm_wday and tm_yday  components
       of the structure are set appropriately, and the other com-
       ponents 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  returns  the specified calendar
       time; If the  calendar  time  cannot  be  represented,  it
       returns -1.

       Difftime  returns  the  difference  between  two  calendar
       times, (time1 - time0), expressed in seconds.

       Declarations of all the functions and externals,  and  the
       ``tm''  structure,  are  in the <time.h> header file.  The
       structure (of  type)  struct  tm  includes  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? */
                   char *tm_zone;   /* abbreviation of timezone name */
                   long tm_gmtoff;  /* offset from UTC in seconds */

       The tm_zone and tm_gmtoff fields exist, and are filled in,
       only if arrangements to do so were made when  the  library
       containing these functions was created.  There is no guar-
       antee that these fields will continue  to  exist  in  this
       form in future releases of this code.

       Tm_isdst is non-zero if summer time is in effect.

       Tm_gmtoff  is  the  offset (in seconds) of the time repre-
       sented from UTC, with positive values indicating  east  of
       the Prime Meridian.


FILES

       /usr/local/etc/zoneinfo             time  zone information
       directory
       /usr/local/etc/zoneinfo/localtime   local time zone file
       /usr/local/etc/zoneinfo/posixrules  used with  POSIX-style
       TZ's
       /usr/local/etc/zoneinfo/GMT         for UTC leap seconds

       If /usr/local/etc/zoneinfo/GMT is absent, UTC leap seconds
       are loaded from /usr/local/etc/zoneinfo/posixrules.


SEE ALSO

       getenv(3), newtzset(3), time(2), tzfile(5)


NOTES

       The return values point to static data; the data is  over-
       written  by  each  call.   The tm_zone field of a returned
       struct tm points to a static array  of  characters,  which
       will also be overwritten at the next call (and by calls to
       tzset).

       Avoid using out-of-range values with mktime  when  setting
       up lunch with promptness sticklers in Riyadh.
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