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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