The Open Group Base Specifications Issue 7
IEEE Std 1003.1, 2013 Edition
Copyright © 2001-2013 The IEEE and The Open Group

#### 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 XBD 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

> XBD 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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