I think you were getting some confusion from respondents because I believe it is more common to store past times as UTC and to then convert to the desired timezone after grabbing from the database.

I have mostly used the Timex library (Timex — timex v3.7.13) to perform this conversion. For example, to convert a UTC time from the database you can use to_datetime/2…

record = Repo.get(id)
Timex.to_datetime(record.inserted_at, "Asia/Calcutta")

UTC works great for past times and it sounds like that is your only concern here. For future times, you might actually want to store the timezone and “wall” time in the database. I use the Calecto calendar_datetime custom type (GitHub - lau/calecto: Adapter for the Calendar library in Ecto · GitHub) to store future event times. This should help protect against timezone changes in between the time the event is stored and when it actually takes place.

As an aside, if someone “really” wanted to store past times in a specific time zone, they could probably do so with the Calecto custom type.