### TZ Environment Variable

This variable is used to describe the time-zone information that the locale will use.

You can set the timezone by calling the tzset function. tzset passes the values held in the TZ environment variable to any other function in the library that may require them (for example, mktime).

The following command sets the standard time zone to CST, sets the daylight saving time zone to CDT, and sets a difference of 6 hours between CDT and Coordinated Universal Time (UTC).

>     SET TZ=CST6CDT

If tzset has not been called, the default is ""0"".

When only the standard time zone is specified, the default difference in hours from UTC is 0 instead of 5.

For the TZ variable, the set command has the following format:

The values for the TZ variable are defined in the following table. The default values given are for the POSIX C locale, the default locale supported by IBM C and C++ Compilers.

Variable | Description | Default value
--- | --- | ---
SSS | Standard-timezone identifier. It must be three characters, must begin with a letter, and can contain spaces. Zone names are determined by local or country convention. For example, EST stands for Eastern Standard Time and applies to parts of North America. | ""
h, m, s | The variable h specifies the difference (in hours) between the standard time zone and CUT, formerly Greenwich mean time (GMT). You can optionally use m to specify minutes after the hour, and s to specify seconds after the minute. A positive number denotes time zones west of the Greenwich meridian; a negative number denotes time zones east of the Greenwich meridian. The number must be an integer value. | 0
DDD | Daylight saving time (DST) zone identifier. It must be three characters, must begin with a letter, and can contain spaces. | ""
sm | Starting month (1 to 12) of DST. | 0
sw | Starting week (-4 to 4) of DST. Use negative numbers to count back from the last week of the month (-1) and positive numbers to count from the first week (1). | 0
sd | Starting day of DST. 0 to 6 if sw != 0 1 to 31 if sw = 0 | 0
st | Starting time (in seconds) of DST. | 0
em | Ending month (1 to 12) of DST. | 0
ew | Ending week (-4 to 4) of DST. Use negative numbers to count back from the last week of the month (-1) and positive numbers to count from the first week (1). | 0
ed | Ending day of DST. 0 to 6 if ew != 0 1 to 31 if ew = 0 | 0
et | Ending time of DST (in seconds). | 0
shift | Amount of time change (in seconds). | 0

If you give values for any of sm, sw, sd, st, em, ew, ed, et, or shift, you must give values for all of them. Otherwise, the entire statement is considered not valid, and the time zone information is not changed.

Application Run-Time Environment Variables
Localization and Locales

Set Windows Run-Time Environment Variables
Set OS/2 Run-Time Environment Variables
Make Your Program International

Default POSIX C Locale