# localtime

## 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.1‐2017 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.1‐2017, _Section 4.16_ , _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_() sets _tzname_ , it shall also set
           _daylight_ and _timezone_.  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.
    


* * *