Home Contents | # TZ Variable | Date/Time | Core4 Lua Commands

## DESCRIPTION

If TZ begins with a colon, it is used as a pathname of a file from which to read the time conversion information.

If TZ does not begin with a colon, it is first used as the pathname of a file from which to read the time conversion information, and, if that file cannot be read, is used directly as a specification of the time conversion information.

When TZ is used as a pathname, if it begins with a slash, it is used as an absolute pathname; otherwise, it is used as a pathname relative to a system time conversion information directory.

When TZ is used directly as a specification of the time conversion information, it must have the following syntax (spaces inserted for clarity):

std offset [dst [offset]] [, rule]

Where:

std and dst | Three or more bytes that are the designation for the standard (std) or summer (dst) time zone. Only std is required; if dst is missing, then summer time does not apply in this locale. Upper and lowercase letters are explicitly allowed. Any characters except a leading colon (':'), digits, comma (','), minus ('-'), plus ('+'), and ASCII NUL are allowed.
offset | Indicates the value one must add to the local time to arrive at Coordinated Universal Time. offset has the form (spaces inserted for clarity): hh [: mm [: ss]] The minutes (mm) and seconds (ss) are optional. The hour (hh) is required and may be a single digit. The offset fol- lowing std is required. If no offset follows dst, summer time is assumed to be one hour ahead of standard time. One or more digits may be used; the value is always interpreted as a decimal number. The hour must be between zero and 24, and the minutes (and seconds) -- if present -- between zero and 59. If preceded by a "-", the time zone shall be east of the Prime Meridian; otherwise it shall be west (which may be indicated by an optional preceding "+").
rule | Indicates when to change to and back from summer time. rule has the form (spaces added for clarity): date / time, date / time where the first date describes when the change from standard to summer time occurs and the second date describes when the change back happens. Each time field describes when, in current local time, the change to the other time is made. The format of date is one of the following (spaces added for clarity):
J n | The Julian day n (1 <= n <= 365). Leap days are not counted; that is, in all years -- including leap years -- February 28 is day 59 and March 1 is day 60. It is impossible to explicitly refer to the occasional February 29.
n | The zero-based Julian day (0 <= n <= 365). Leap days are counted, and it is possible to refer to February 29.
M m . n . d | Day d (1 <= d <= 6) of week n (1 <= n <= 5) of month m (1 <= m <= 12), where week 5 means "the last d day in month m" which may occur in either the fourth or the fifth week. Week 1 is the first week in which the dth day occurs. Day zero is Sunday. The time has the same format as offset except that no leading sign ("-" or "+") is allowed. The default, if time is not given, is 02:00:00.

## EXAMPLES

    CET-1CEST-2,M3.5.0/02:00:00,M10.5.0/03:00:00

Timezone specification for central europe. For example purposes only. It is recommended to just set TZ to Europe/Berlin.

## NOTES

Some default rule files are provided with the standard SDK, but feel free to add your own. Note that the Core4 SDK supports gzip compression of the zoneinfo files.

For example, if TZ is Europe/Berlin, then the actual file would be found at /etc/zoneinfo/Europe/Berlin.

The reason why some zoneinfo files are so large is that there might be no single daylight savings rule for a specific location. Politics tends to change these rules every now and then. Therefore, the zoneinfo file contains not only the current rule, but also rules for the past.

This documentation page is courtesy of the OpenBSD tzset(3) man-page.