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PROLOG

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of
       this interface may differ (consult the corresponding Linux  manual  page  for  details  of
       Linux behavior), or the interface may not be implemented on Linux.

NAME

       localtime, localtime_r — convert a time value to a broken-down local time

SYNOPSIS

       #include <time.h>

       struct tm *localtime(const time_t *timer);
       struct tm *localtime_r(const time_t *restrict timer,
           struct tm *restrict result);

DESCRIPTION

       For  localtime():  The  functionality described on this reference page is aligned with the
       ISO C standard. Any conflict  between  the  requirements  described  here  and  the  ISO C
       standard is unintentional. This volume of POSIX.1‐2008 defers to the ISO C standard.

       The  localtime()  function shall convert the time in seconds since the Epoch pointed to by
       timer into a broken-down time, expressed as a local time. The function  corrects  for  the
       timezone  and any seasonal time adjustments.  Local timezone information is used as though
       localtime() calls tzset().

       The relationship between a time in  seconds  since  the  Epoch  used  as  an  argument  to
       localtime() and the tm structure (defined in the <time.h> header) is that the result shall
       be as specified in the expression given in the definition of seconds since the Epoch  (see
       the  Base  Definitions  volume  of  POSIX.1‐2008,  Section  4.15, Seconds Since the Epoch)
       corrected for timezone and any seasonal time adjustments, where the names in the structure
       and in the expression correspond.

       The same relationship shall apply for localtime_r().

       The localtime() function need not be thread-safe.

       The  asctime(), ctime(), gmtime(), and localtime() functions shall return values in one of
       two static objects: a broken-down time structure and an array of type char.  Execution  of
       any  of the functions may overwrite the information returned in either of these objects by
       any of the other functions.

       The localtime_r() function shall convert the time in seconds since the Epoch pointed to by
       timer  into  a  broken-down  time  stored  in  the  structure  to which result points. The
       localtime_r() function shall also return a pointer to that same structure.

       Unlike localtime(), the  localtime_r()  function  is  not  required  to  set  tzname.   If
       localtime_r() does not set tzname, it shall not set daylight and shall not set timezone.

RETURN VALUE

       Upon successful completion, the localtime() function shall return a pointer to the broken-
       down time structure.  If an error is detected, localtime() shall return a null pointer and
       set errno to indicate the error.

       Upon  successful completion, localtime_r() shall return a pointer to the structure pointed
       to by the argument result.  If an error is detected, localtime_r()  shall  return  a  null
       pointer and set errno to indicate the error.

ERRORS

       The localtime() and localtime_r() functions shall fail if:

       EOVERFLOW
              The result cannot be represented.

       The following sections are informative.

EXAMPLES

   Getting the Local Date and Time
       The  following example uses the time() function to calculate the time elapsed, in seconds,
       since January 1, 1970 0:00 UTC (the Epoch), localtime() to convert that value to a broken-
       down time, and asctime() to convert the broken-down time values into a printable string.

           #include <stdio.h>
           #include <time.h>

           int main(void)
           {
               time_t result;

               result = time(NULL);
               printf("%s%ju secs since the Epoch\n",
                   asctime(localtime(&result)),
                       (uintmax_t)result);
               return(0);
           }

       This example writes the current time to stdout in a form like this:

           Wed Jun 26 10:32:15 1996
           835810335 secs since the Epoch

   Getting the Modification Time for a File
       The  following  example  prints the last data modification timestamp in the local timezone
       for a given file.

           #include <stdio.h>
           #include <time.h>
           #include <sys/stat.h>

           int
           print_file_time(const char *pathname)
           {
               struct stat statbuf;
               struct tm *tm;
               char timestr[BUFSIZ];

               if(stat(pathname, &statbuf) == −1)
                   return −1;
               if((tm = localtime(&statbuf.st_mtime)) == NULL)
                   return −1;
               if(strftime(timestr, sizeof(timestr), "%Y-%m-%d %H:%M:%S", tm) == 0)
                   return −1;
               printf("%s: %s.%09ld\n", pathname, timestr, statbuf.st_mtim.tv_nsec);
               return 0;
           }

   Timing an Event
       The following example gets the current time, converts it to a string using localtime() and
       asctime(),  and  prints it to standard output using fputs().  It then prints the number of
       minutes to an event being timed.

           #include <time.h>
           #include <stdio.h>
           ...
           time_t now;
           int minutes_to_event;
           ...
           time(&now);
           printf("The time is ");
           fputs(asctime(localtime(&now)), stdout);
           printf("There are still %d minutes to the event.\n",
               minutes_to_event);
           ...

APPLICATION USAGE

       The localtime_r() function is thread-safe and returns values  in  a  user-supplied  buffer
       instead of possibly using a static data area that may be overwritten by each call.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       asctime(),  clock(),  ctime(),  difftime(),  getdate(),  gmtime(),  mktime(),  strftime(),
       strptime(), time(), tzset(), utime()

       The Base Definitions volume of  POSIX.1‐2008,  Section  4.15,  Seconds  Since  the  Epoch,
       <time.h>

COPYRIGHT

       Portions  of  this  text  are  reprinted  and  reproduced in electronic form from IEEE Std
       1003.1, 2013 Edition, Standard for Information Technology  --  Portable  Operating  System
       Interface  (POSIX),  The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the
       Institute of Electrical and Electronics Engineers, Inc  and  The  Open  Group.   (This  is
       POSIX.1-2008  with  the  2013  Technical  Corrigendum  1  applied.)  In  the  event of any
       discrepancy between this version and the original IEEE and The Open  Group  Standard,  the
       original  IEEE  and The Open Group Standard is the referee document. The original Standard
       can be obtained online at http://www.unix.org/online.html .

       Any typographical or formatting errors that appear in this page are most  likely  to  have
       been  introduced  during  the conversion of the source files to man page format. To report
       such errors, see https://www.kernel.org/doc/man-pages/reporting_bugs.html .