2.1.8.25 localtime

1 Description
2 Syntax
3 Parameters
4 Return
5 Examples
6 Remark
7 See Also
8 Header to Include
9 Reference

Description

Convert a time stored as a time_t value and stores the result in a structure of type tm.

Syntax

TM * localtime( const time_t * timer )

Parameters

timer: [input] Pointer to stored time

Return

localtime returns a pointer to the structure result. If the value in timer represents a date before midnight, January 1, 1970, localtime returns NULL. The fields of the structure type tm store the following values, each of which is an int:

tm_sec: Seconds after minute (0 - 59)

tm_min: Minutes after hour (0 - 59)

tm_hour:Hours after midnight (0 - 23)

tm_mday:Day of month (1 - 31)

tm_mon: Month (0 - 11; January = 0)

tm_year:Year (current year minus 1900)

tm_wday:Day of week (0 - 6; Sunday = 0)

tm_yday:Day of year (0 - 365; January 1 = 0)

tm_isdst:Positive value if daylight saving time is in effect; 0 if daylight saving time is not in effect; negative value if status of daylight saving time is unknown. The C run-time library assumes the United States's rules for implementing the calculation of Daylight Saving Time (DST).

Examples

EX1

void Localtim_Ex1()
{
    struct tm *newtime;
    time_t aclock;
    time( &aclock );                 // Get time in seconds 
 
    newtime = localtime( &aclock );  // Convert time to struct tm form 

    // Print local time as a string 
    printf( "The current date and time are: %s", asctime( newtime ) );
}

Remark

The localtime function converts a time stored as a time_t value and stores the result in a structure of type tm. The long value timer represents the seconds elapsed since midnight (00:00:00), January 1, 1970,

coordinated universal time (UTC). This value is usually obtained from the time function.

gmtime, mktime, and localtime all use a single statically allocated tm structure for the conversion. Each call to one of these routines destroys the result of the previous call.

localtime corrects for the local time zone if the user first sets the global environment variable TZ. When TZ is set, three other environment variables (_timezone, _daylight, and _tzname)

are automatically set as well. See _tzset for a description of these variables. TZ is a Microsoft extension and not part of the ANSI standard definition of localtime.

Note The target environment should try to determine whether daylight saving time is in effect.