https://codeofmatt.com/on-the-timing-of-time-zone-changes/

I think the right thing is to store times with the timezone the user wanted when they created the time. You can often use defaults or other UX niceties to streamline specifying TZ, but not always.

Also, if you'll want to unambiguously know the timestamp's exact point in time at some point (like for comparison with other dayetimes), you should save the offset from UTC alongside the actual datetime. Otherwise, around clock changes like "fall back" you cannot tell if you're seeing 2 AM for the first or second time.

This is the best I've come to trying to piece datetime storage together. If someone has better advice, I'd love to hear it.

For more of my theory on timezone handling and the sources I've used to help me think it through, see http://howicode.nateeag.com/dates-and-times.html .