IBM® AIX® supports two time zone formats: Portable Operating System Interface (POSIX) and Olson.
POSIX is the traditional format of setting the time zone and Olson is the latest, simple, easy to understand format.
This Olson time zone format maintains a database, which is a collaborative compilation of information about the world's time zones.
This database is a set of text files containing the rules and zone transitions organized continent-wise and is periodically updated and published by Internet Assigned Numbers Authority (IANA).
This information is in human readable format and can be used for compiling it into binary files using zone information compiler.
This article helps you to understand how to update the Olson time zone database on IBM AIX whenever the government announces any change to time zone boundaries, UTC offsets, and daylight saving rules.
The Olson time zone database maintains the history of the time zone and Daylight Saving Time (DST)-related changes in a binary file or each time zone under the /usr/share/lib/zoneinfo directory in AIX.
When a government changes a time zone offset or DST rule, these binaries need to updated with the latest information.
But most of the times, government announces the change in a short time, which leaves very less time for the customers to update their systems.
During such short time notices, instead of waiting for the interim fix process, customer can update the Olson database as mentioned below.
Note: The following update process is applicable from AIX version 7.200- and 7100- onwards. This zone recently announced that it ends DST on 29 October 2016 and not 21 October 2016 at .
Refer to the following demo: command gives a clear picture of DST change timing for the particular time zone.
For example, in Figure 1, the first two lines explain the scenario when daylight saving is enabled and the last two lines explain the scenario when it is disabled.