Glad to hear you worked it out, but I don’t understand how your formula works. For example, 25569 days is roughly 70 years, not 50 (20201970). But who am I to question it if it solves your problem?
I will say that any formula for converting ‘seconds since Unix epoch’ to today’s date/time which doesn’t account for leap years will not be robust enough to use in the general case.
How are you doing the computation (spreadsheet, program [what language])? The time in seconds (not milliseconds) since the Unix epoch is a very common thing in the computing world and there should be a function to do the calculation for you — in both directions, in fact. No sense reinventing the wheel!
As to how I did the conversion, it’s a trivial 1line command in Linux:
> TZ='UTC' date d @1605826471
Thu Nov 19 22:54:31 UTC 2020
If I wanted it in my local timezone, I’d just leave off the leading “TZ=’UTC'” part.
But of course, when doing it programmatically, I use the various ‘time’ library’s functions.
