On 2026-03-07 15:25, Steffen Nurpmeso via tz wrote:
It seems to me it uses ICU
On my Ubuntu 25.10 platform, my email client (Thunderbird) uses the GNU C library to read TZif data. I was talking about that usage, not any ICU usage. On my platform ICU has its own copy of the time zone data, and this copy can be out of sync with tzdata's copy on the same platform. Although failures due to mismatch are rare, they can be a mess when they do happen, and that has partly inspired the current thread. For more, see the following (tz-link.html refers to this page): https://unicode-org.github.io/icu/userguide/datetime/timezone/#updating-the-... PS. Ubuntu makes matters even more complicated by using snaps, each of which can have their own private copy of both tzdata and CLDR, and all these copies can be out of date and/or mismatch each other! But that's Ubuntu's problem, not TZDB's or CLDR's.