The Open Group Base Specifications Issue 6
IEEE Std 1003.1, 2004 Edition
Copyright © 2001-2004 The IEEE and The Open Group, All Rights reserved.

NAME

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

SYNOPSIS

#include <time.h>

[XSI] [Option Start] extern int daylight;
extern long timezone;
[Option End]
[CX] [Option Start] extern char *tzname[2];
void tzset(void); [Option End]

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, 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.

[XSI] [Option Start] 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. [Option End]

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 ALSO

ctime(), localtime(), mktime(), strftime(), the Base Definitions volume of IEEE Std 1003.1-2001, Chapter 8, Environment Variables, <time.h>

CHANGE HISTORY

First released in Issue 1. Derived from Issue 1 of the SVID.

Issue 6

The example is corrected.

End of informative text.

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