@sjpiper145 "Use a calendar with different timezones to plan."

Yes well, there was the time I was phoning a hotel in Hawaii from Sydney trying to book a room. Which was immensely complicated by the facts that (a) there was an international date line between us and (b) my flight was due to arrive just after midnight (so, say, an arrival on the 19th so the hotel booking was needed for the 18th).

At some point the hotel asked me something like "do you mean the day after tomorrow?" and I hadn't the remotest clue, I just couldn't answer that question.