11.4 Time-Zone Conversion Rule Files

The time-zone files pointed to by the SYS$LOCALTIME and SYS$POSIXRULES logicals are part of a public-domain, time-zone support package installed on OpenVMS Version 7.0 and higher systems.

This support package includes a series of source files that describe the timezone conversion rules for computing local time from UTC in world-wide timezones. OpenVMS Version 7.0 and higher systems provide a time-zone compiler called ZIC. The ZIC compiler compiles time-zone source files into binary files that the DEC C RTL reads to acquire time-zone conversion specifications. For more information on the format of these source files see the OpenVMS system documentation for ZIC.

The time-zone files are organized as follows:

The root time-zone directory is: SYS$COMMON:[SYS$TIMEZONE.SYSTEM]. The system logical SYS$TZDIR is set during installation to point to this area.
Time-zone source files are found in: SYS$COMMON:[SYS$TIMEZONE.SYSTEM.SOURCES].
Binary time-zone files use SYS$COMMON:[SYS$TIMEZONE.SYSTEM] as their root directory. Some binaries reside in this directory while others reside in its subdirectories.
Binaries residing in subdirectories are time-zone files that represent specific time zones in a larger geographic area. For example, SYS$COMMON:[SYS$TIMEZONE.SYSTEM] contains a subdirectory for the United States and a subdirectory for Canada, because each of these geographic locations contains several time zones. Each time zone in the US is represented by a time-zone file in the Unites States subdirectory. Each time zone in Canada is represented by a time-zone file in the Canada subdirectory.

Several of the time-zone files have names based on acronyms for the areas that they represent. Table 11-2 lists these acronyms.

Table 11-2 Time-zone Filename Acronyms

Time-Zone Acronym	Description
CET	Central European Time
EET	Eastern European Time
Factory	Specifies No Time Zone
GB-Eire	Great Britain/Ireland
GMT	Greenwich Mean Time
NZ	New Zealand
NZ-CHAT	New Zealand, Chatham Islands
MET	Middle European Time
PRC	Peoples Republic of China
ROC	Republic of China
ROK	Republic of Korea
SystemV	Specific to System V operating system
UCT	Universal Coordinated Time
US	United States
UTC	Universal Coordinated Time
Universal	Universal Coordinated Time
W-SU	Middle European Time
WET	Western European Time

A mechanism is available for you to define and implement your own time-zone rules. For more information, see the OpenVMS system documentation on the ZIC compiler and the description of tzset in the reference section of this manual.

Also, the SYS$LOCALTIME and SYS$POSIXRULES system logicals can be redefined to user-supplied time zones.

Previous Page | Next Page | Table of Contents | Index