Hi: Recently, I wanted to write a program to watch the change of timezone database. I got newest version from this address: https://data.iana.org/time-zones/releases/tzdata2021a.tar.gz. I used zic (version: zic (tzcode) 2020c, system: CentOS Linux release 7.6.1810 (Core)) to generate the zoneinfo. I pick up some zones with local timeto calculate utc time to verify the changes using both the new and currently used version tzdata, here is diff: zone local time by 2021a utc time by 2020d utc time America/Adak 2022-11-01 00:00:00 2022-11-01 09:00:00 2022-11-01 10:00:00 America/Anchorage 2022-11-01 00:00:00 2022-11-01 08:00:00 2022-11-01 09:00:00 America/Asuncion 2022-10-01 00:00:00 2022-10-01 04:00:00 2022-10-01 03:00:00 America/Atka 2022-11-01 00:00:00 2022-11-01 09:00:00 2022-11-01 10:00:00 Those zones are not changed from version 2020d to 2021a. I am very confused and not sure if I generated the zoneinfo in the right way. Here was what do: # mkdir zoneinfo # cd tzdata2021a # zic -d ../zoneinfo -L ./leapseconds africa antarctica asia australasia europe northamerica southamerica etcetera backward factory I was wondering if you could provide me some help. I really appreciate your reply. Sincerely, wangmm