Dates remain an amusing challenge in software. Got a complaint from a customer that they bought a subscription at 6pm their time on the 31st Jan… but got a receipt with the date as 1 Feb. This is wrong - and they are right! But from the server’s POV, the date is right!

Imagine you are building a system: how do you build it: - To use the client’s timezone / time settings - but this opens up all kinds of interesting challenges (including eg past/future dates!) - To convert the receipt to the client’s timezone: but then what happens when the same user eg travels. Do all their receipts change dates? - To use UTC (what is happening here): consistent but then wrong from the client POV It’s a hard problem!