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] extern int daylight;
> extern long timezone;
> ``
> ``[CX] 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, 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] 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.

#### 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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