We are having a system running on servers having EET time zone, In 2023 before DST changes in Egypt, Java (jre8) and Joda(2.12.5) libraries were updated and it worked fine with EEST time zone. this year2024 Egypt is again doing DST and changing time zone to EEST. Do we need to apply a new patch for java-8 and Joda libraries to make it work, or previous one should work as expected

tl;dr

If the politicians have changed the rules for a time zone of interest to the stakeholders of your systems, then yes of course you must update all the tzdata files in all the places where they exist.

• If you care about Africa/Cairo, and the Egyptian politicians have changed the rules, then you must update all copies of tzdata everywhere.
• If the politicians of Ecuador change the rules for Pacific/Galapagos, but your stakeholders have no interest in Galápagos Islands, then you can leave your existing tzdata files in place.

Details

If the politicians have changed the rules of a time zone of interest to you, then of course you must update the tzdata.

A tzdata file is simply text, listing every time zone around the globe along with the rules listing the past, preset, and future changes to the offset from UTC used by the people of a particular region as decoded by their politicians. So no magic here. If the politicians have changed the rules, then your tzdata text file is invalid. You must replace each and every copy of the tzdata text file on your machines.

Beware: Politicians in different places have been unwisely making such changes with shockingly little forewarning.

Note that you likely have copies of tzdata in multiple places:

• Java Virtual Machine (JDK, JRE)
• Libraries such as Joda-Time
• Database engine such as Postgres
• Host operating system (OS)

If updating one, update all.

If the politicians have made no changes to the time zones of interest to you, then no need to update tzdata.

But it certainly does not hurt to update tzdata. New versions arrive a few times a year, typically.

The tzdata is published by the IANA. At this page you can see the latest update. And there you can sign up for email announcements of new releases.

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Beware: 2-4 letter pseudo-zones like EEST, IST, and CST are not actual time zones. These pseudo-zones are not standardized, and are not even unique! Use these only when localizing text for presentation to the user. Never use these in your technical discussions, logic, and data.

Real time zones have a name in format of Continint/Region such as Africa/Cairo, Europe/Paris, Pacific/Auckland.