If your friend lives in London it may be useful to have that associated timezone so that you can be sure to message them that day in their timezone. They might better appreciate a message from SF sent on March 10th at 9PM "early that morning in London" than March 11th at 9PM "a day late".
replyA lot of that gets back to why Temporal adds so many different types, because there are different uses for time zone information and being clear how you shift that information can make a big difference. (A birthday is a PlainDate at rest, but when it is time to send them an ecard you want the ZonedDateTime of the recipient's time zone to find the best time to send it.)
His birthday is always all day. The question is where he is. If he travels to Japan his birthday won't change - even if he was born late at night and thus it would be a different day if he was born in Japan.
replyThe other fun ones are daily recurring events for e.g. taking some medication. You take the last one at 10pm before going to bed. You go on a trip which moves you three hours east. Now your calendar helpfully reminds you to take your meds at 1 am.
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