IANA Time Zone Data
Every release of Azul Zulu bundles a specific version of the IANA time zone database (tzdata), the source used to compute time zone offsets and daylight saving time (DST) transitions in java.time and java.util.TimeZone.
Because governments change DST rules and zone boundaries throughout the year, the tzdata version shipped with a JDK build can go stale between releases.
If your application shows the wrong local time, an incorrect UTC offset, or a DST transition on the wrong date, check the tzdata version your release carries below, then update your time zone data with the Timezone Updater tool if needed — you don’t have to reinstall or upgrade the JDK to do so.
Which Tzdata Version Does My Release Carry?
Each release’s Release Notes list a (tz) Update Timezone Data to <version> entry whenever that release’s OpenJDK bug-fix list includes a tzdata bump. This list is scoped to that release’s own fixes, not a running cumulative log. A release with no such entry did not necessarily keep the previous version; it simply picked up no tzdata-related fix from upstream OpenJDK that cycle. Treat the table below as "confirmed bumps," not a complete continuous history, and use the runtime check further down to confirm the version an actual installation is running.
| Release | Tzdata Version |
|---|---|
September 2026 |
2026b |
July 2026 |
2026b |
April 2026 |
2026a |
January 2026 |
2025b |
October 2025 |
2025b |
July 2025 |
2025b |
April 2025 |
2025a |
January 2025 |
2024b |
October 2024 |
2024a |
July 2024 |
2024a |
April 2024 |
2024a |
January 2024 |
2023c |
Checking the Tzdata Version of an Installed JDK
To confirm the tzdata version a JVM is actually running, without relying on the table above, run a small snippet, for instance, with jshell:
$ jshell
| Welcome to JShell -- Version 26
| For an introduction type: /help intro
jshell> System.out.println(java.time.zone.ZoneRulesProvider.getVersions("UTC").keySet());
[2026b]
jshell> /exit
| Goodbye
This prints the tzdata version(s) the JVM’s tzdb.dat was built from (for example, [2026b]).