NAME | SYNOPSIS | DESCRIPTION | ATTRIBUTES | SEE ALSO
#include <time.h>void tzset(void);
extern char *tzname[2];
The tzset function uses the value of the environment variable TZ to set time conversion information used by localtime(3STDC), ctime(3STDC), strftime(3STDC), and mktime(3STDC).
When tzset is called, the time zone names contained in the external variable tzname are set according to the contents of TZ.
The format of TZ is: stdoffset[dst[offset][,start/[time],end[/time]]]
where:
Indicate no less than three and no more than TZNAME_MAX bytes, which designate the standard (std) and daylight saving time (dst) time zones. Only std is required,; if dst is not specififed, daylight saving time does not apply in this area. Upper- and lowercase letters are allowed. Any characters except a leading colon (:), digits, a comma (,), a minus (-), a plus (+) or a null character are allowed.
Indicates the value to be added to the local time to arrive at Coordinated Universal Time. The offset has the form: hh[:mm[:ss]]. The minutes (mm) and seconds (ss) are optional. The hour (hh) is required and may be a single digit. The offset following std is required. If no offset follows dst , daylight saving time is assumed to be one hour ahead of standard time. One or more digits may be used; the value is always interpreted as a decimal number. The hour must be between 0 and 24, and the minutes and seconds (if present) between 0 and 59. Entering a value that is out of range may produce unpredictable results. If preceded by a "-", the time zone is east of the Prime Meridian; otherwise it is west (which may be indicated by an optional preceding "+" sign).
Indicates when to change to and back from daylight saving time, where start/time describes when the change from standard time to daylight saving time happens, and end/time describes when the change back happens. Each time field describes when, in current local time, the change to the other time is made. The formats of start and end are one of the following:
The Julian day n (1 <= n <= 365). Leap days are not counted. That is, in all years, February 28 is day 59 and March 1 is day 60. It is impossible to refer to February 29.
The zero-based Julian day (0 <= n <= 365). Leap days are counted, and it is possible to refer to February 29.
The dth day, (0 <= d <= 6) of week n of month m of the year (1 <= n <= 5, 1 <= m <= 12), where week 5 means "the last d-day in month m" which may occur in either the fourth or the fifth week). Week 1 is the first week in which the dth day occurs. Day zero is Sunday.
Implementation-specific defaults are used for start and end if these optional fields are not given. The time has the same format as offset except that no leading sign ("-" or "+") is allowed. The default, if time is not given is 02:00:00.
See attributes(5) for descriptions of the following attributes:
ATTRIBUTE TYPE | ATTRIBUTE VALUE |
---|---|
Interface Stability | Evolving |
NAME | SYNOPSIS | DESCRIPTION | ATTRIBUTES | SEE ALSO