Contributing Advent 21: Timezone database
Timezones have always been a pain, and Daylight Saving(s) time does not make it a lot easier. Then of course you have governments that decide to change the rules. Often that is done nicely in advance, but once in a while the rule changes are announced at the absolutely last moment, or, sometimes even after the new rules have come into effect. To track the craziness, have a look at Time Zone News, and this image to see how many different rules there are!