TZSET(3P) POSIX Programmer's Manual TZSET(3P)PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the corresponding
Linux manual page for details of Linux behavior), or the interface may
not be implemented on Linux.
NAME
daylight, timezone, tzname, tzset — set timezone conversion information
SYNOPSIS
#include <time.h>
extern int daylight;
extern long timezone;
extern char *tzname[2];
void tzset(void);
DESCRIPTION
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, imple‐
mentation-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
POSIX.1‐2008, 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 Univer‐
sal Time (UTC) and local standard time.
RETURN VALUE
The tzset() function shall not return a value.
ERRORS
No errors are defined.
The following sections are informative.
EXAMPLES
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 │
└───────────┴────────────┘
APPLICATION USAGE
None.
RATIONALE
None.
FUTURE DIRECTIONS
None.
SEE ALSOctime(), localtime(), mktime(), strftime()
The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment
Variables, <time.h>
COPYRIGHT
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
cal and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the source
files to man page format. To report such errors, see https://www.ker‐
nel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 TZSET(3P)
