DAYLIGHT(3) Library Functions Manual DAYLIGHT(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 XBD V1_chap08(7).

The tzset () function also shall set the external variable daylight 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)

XBD V1_chap08(7), <time.h>

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

The example is corrected.

January 1, 2013 posix.fail