I just slipped this across to UX because I am realizing you are sharing feedback here about a limitation we have in Discourse with the way time zones work.
I myself shift location frequently between Berlin and Seattle. When I am in Berlin and select Use Current Timezone in my preferences it selects Europe/Berlin, but when I am in Seattle it selects America/Los_Angeles. This is because there are a limited number of available timezones to choose from. It’s always been this way.
A UX improvement would be to allow the user to enter in/select their own location and then for Discourse to map it to the time zone automatically. This is how it works in most operating systems, for example.
I also think it would be helpful for Discourse to prompt the user to change the timezone when the timezone configured is different from the current timezone, without having to go to their user preferences and find the setting.