B    Time Zone Enhancements

The naming convention for /etc/zoneinfo/ time zone directories and files has changed from the former COUNTRY/ZONE style (for example, US/Eastern) to the more stable AREA/LOCATION format (for example, America/New_York), where AREA is the name of a continent or ocean, and LOCATION is the name of a specific location (major city, locale, and so on within that region). All previous /etc/zoneinfo/ directories and time zone files are available, for compatibility; however, many of the files are now hard links to their renamed counterparts. Obsolete time zone mappings are provided for reference in Table B-2.

The time zone data file format has been expanded to handle more complex transition rules. (See the tzfile(4) reference page for details.) The zic compiler zdump command and several time-related functions in the standard C library have been updated to support the expanded time zone data file format.

While the time zone data file format has been expanded to support additional transition rules, time zone data files created on prior versions of the operating system will work without recompilation. This provides support for user-generated time zone data files, which may or may not have original source code.

Conversely, static applications created on prior versions of the operating system and that reference time zone data will be able to process most of the new time zone data files in the /etc/zoneinfo/ directory. They will not take advantage of the new time zone data file extensions, but will still read and process the portions of these files they did previously. However, due to the expanded number of time transition types available in the new time zone data files, certain older static applications will not be able to read the new time zones listed in Table B-1.

Table B-1:  Incompatible New Time Zones

Enablers were added to Version 4.0D of the operating system to allow the new time zones to be read; therefore, static applications built on Version 4.0D or later releases will not have problems with these files. It is important to note that none of the time zones listed in Table B-1 existed on versions of the operating system prior to Version 5.0. It is, therefore, unlikely that any existing applications reference any of the time zones listed.

Shared applications are not affected by the issue above, because they automatically pick up the new time zone data file support in Version 4.0D and later versions of the operating system.

Table B-2 provides a mapping of the old time zones to the new time zones.

Table B-2:  Mapping of the Old Time Zones to New Time Zones