#include <time.h>
extern int daylight;
extern long timezone;
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() , localtime() , mktime() , and strftime() . If TZ is absent from the environment, implementation-defined default timezone information shall be used.
The tzset() function shall set the external variable tzname as follows:
tzname[0] = "std"; tzname[1] = "dst";
where std and dst are as described in the Base Definitions volume of IEEE Std 1003.1-2001, Chapter 8, Environment Variables.
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 timezone 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.
The following sections are informative.
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 |
ctime() , localtime() , mktime() , strftime() , the Base Definitions volume of IEEE Std 1003.1-2001, Chapter 8, Environment Variables, <time.h>