The Time Zone Database Package (tzdata) review for 2023

The Time Zone Database Package (tzdata) provides Red Hat Enterprise Linux (RHEL) with the time zone information needed for all applications or runtimes in the operating system to print local time correctly. The GNU C Library (glibc) uses the tzdata package, so APIs like strftime() work correctly, while applications such as /usr/bin/date use this information to print the local date.

The tzdata package contains the data files describing current and historic transitions for various time zones worldwide. This data represents changes required by local governments, time zone boundary changes, UTC offsets and daylight saving time (DST).

tzdata has not seen any significant time zone changes since March, but this year began with three updates from the upstream project in one week.

In fact, two of the updates were so close together that we combined them to reduce customer impact. Newer updates have superseded other updates that are still in testing. Frequently, this is a result of local governing bodies making last-minute changes around the start or end of DST.

For example, Asia/Hebron and Asia/Gaza time zones were scheduled to transition to summer time on March 25th, 2023. On March 22nd, the upstream project was notified that the summer time transition would be delayed until April 29th. Upstream tzdata quickly released an update late on March 22nd.

On March 23rd, as Red Hat Engineering was building and performing initial testing of tzdata-2023a, we were notified of another impending update to the Asia/Beirut time zone. On March 24th, the upstream project released this update, and Red Hat Engineering began working on tzdata-2023b. tzdata-2023b included all of the planned changes in tzdata-2023a and the change for Asia/Beirut.

On Sunday, March 26, world news broadcast that there was confusion regarding the Asia/Beirut time zone change. After discussions within the local government, it was decided that the change was invalid, and further discussion was needed within the government.

Red Hat released tzdata-2023b at that point, providing all pending updates for Asia/Hebron, Asia Gaza, Africa/Casablanca and Africa/Cairo. This update also included the debated change for Asia/Beirut, pending a decision by the local government on how to proceed. Once it was determined that Asia/Beirut would not be moving DST forward to April, Red Hat released tzdata-2023c, reverting the change for Asia/Beirut.

How can we avoid these confusing situations in the future? The biggest factor is requiring organization by local governing bodies to plan changes ahead, preferably at least a year in advance. Change notification should be sent to the upstream project (tz@iana.org). Whenever possible, include links to official documents recording the change.

For more details on changes in tzdata during 2023, see the updated NEWS file included in each release. For the latest status on Red Hat tzdata updates, follow the Red Hat Enterprise Linux Timezone Data (tzdata) - Development Status Page.