While there, I note that fixTimezone() contains some errors.

UTC cannot be a shortcut for America/Los Angeles. The two time zones are 8 hours apart! There are a few countries running UTC year-long. If you really want UTC to be an alias, use Africa/Abidjan or Atlantic/Reykjavik, for instance.

CEST (UTC+2) is translated into Europe/Madrid which is right during summer but not during Winter, where Europe/Madrid is CET (UTC+1).