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TZSET(3P) POSIX Programmer's Manual TZSET(3P)
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.
daylight, timezone, tzname, tzset — set timezone conversion
information
#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(3p),
localtime(3p), mktime(3p), and strftime(3p). 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
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 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 │
└───────────┴────────────┘
None.
None.
None.
ctime(3p), localtime(3p), mktime(3p), strftime(3p)
The Base Definitions volume of POSIX.1‐2008, Chapter 8, Environment
Variables, time.h(0p)
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 Electrical 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.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2013 TZSET(3P)
Pages that refer to this page: time.h(0p), daylight(3p), localtime(3p), mktime(3p), strftime(3p), timezone(3p)