TZSET(3) Library Functions Manual TZSET(3)

daylight timezone tzname tzset — set timezone conversion information

#include <time.h>

[XSI] extern int daylight;
extern long timezone;
[CX] extern char *tzname[2];
void tzset(void);

The tzset () function shall use the value of the environment variable TZ to set time conversion information used by ctime(3) , localtime(3) , mktime(3) , and strftime(3). If TZ is absent from the environment, implementation-defined default timezone information shall be used.

The tzset () function shall set the external variable as follows:

tzname[0] = "std";
tzname[1] = "dst";

where and are as described in the Base Definitions volume of IEEE Std 1003.1-2001 (“POSIX.1”), xbd_chap08(7).

The tzset () function also shall set the external variable to 0 if Daylight Savings Time conversions should never be applied for the timezone in use; otherwise, non-zero. The external variable shall be set to the difference, in seconds, between Coordinated Universal Time (UTC) and local standard time.

The tzset () function shall not return a value.

No errors are defined.

Example TZ variables and their timezone differences are given in the table below:

TZ timezone
EST5EDT 5*60*60
GMT0 0*60*60
JST-9 -9*60*60
MET-1MEST -1*60*60
MST7MDT 7*60*60
PST8PDT 8*60*60

None.

None.

None.

ctime(3), localtime(3), mktime(3), strftime(3), the Base Definitions volume of IEEE Std 1003.1-2001 (“POSIX.1”), xbd_chap08(7), <time.h>

First released in Issue 1. Derived from Issue 1 of the SVID.

The example is corrected.

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January 1, 2004 posix.fail