1TZSET(3P)                  POSIX Programmer's Manual                 TZSET(3P)
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PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
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NAME

12       daylight, timezone, tzname, tzset - set timezone conversion information
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SYNOPSIS

15       #include <time.h>
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19       extern int daylight;
20       extern long timezone;
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23       extern char *tzname[2];
24       void tzset(void);
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DESCRIPTION

28       The tzset() function shall use the value of the environment variable TZ
29       to  set  time  conversion  information  used  by  ctime(), localtime(),
30       mktime(), and strftime() . If TZ is absent from the environment, imple‐
31       mentation-defined default timezone information shall be used.
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33       The tzset() function shall set the external variable tzname as follows:
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36              tzname[0] = "std";
37              tzname[1] = "dst";
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39       where  std  and  dst are as described in the Base Definitions volume of
40       IEEE Std 1003.1-2001, Chapter 8, Environment Variables.
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42       The tzset() function also shall set the external variable daylight to 0
43       if  Daylight  Savings  Time conversions should never be applied for the
44       timezone in use; otherwise, non-zero. The  external  variable  timezone
45       shall be set to the difference, in seconds, between Coordinated Univer‐
46       sal Time (UTC) and local standard time.
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RETURN VALUE

49       The tzset() function shall not return a value.
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ERRORS

52       No errors are defined.
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54       The following sections are informative.
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EXAMPLES

57       Example TZ variables and their timezone differences are  given  in  the
58       table below:
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60                                TZ          timezone
61                                EST5EDT     5*60*60
62                                GMT0        0*60*60
63                                JST-9       -9*60*60
64                                MET-1MEST   -1*60*60
65                                MST7MDT     7*60*60
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67                                PST8PDT     8*60*60
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APPLICATION USAGE

70       None.
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RATIONALE

73       None.
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FUTURE DIRECTIONS

76       None.
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SEE ALSO

79       ctime(), localtime(), mktime(), strftime(), the Base Definitions volume
80       of IEEE Std 1003.1-2001, Chapter 8, Environment Variables, <time.h>
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83       Portions of this text are reprinted and reproduced in  electronic  form
84       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
85       -- Portable Operating System Interface (POSIX),  The  Open  Group  Base
86       Specifications  Issue  6,  Copyright  (C) 2001-2003 by the Institute of
87       Electrical and Electronics Engineers, Inc and The Open  Group.  In  the
88       event of any discrepancy between this version and the original IEEE and
89       The Open Group Standard, the original IEEE and The Open Group  Standard
90       is  the  referee document. The original Standard can be obtained online
91       at http://www.opengroup.org/unix/online.html .
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95IEEE/The Open Group                  2003                            TZSET(3P)
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