[busterarm]

What was this like...1990?

This is 2017. Are you not putting all of your transactions in an ordered table in a database with creation timestamps? That information should not be lost and should be easy to figure out, in UTC. Figuring out the conversion of some other time/date is a solved problem.

There should never be a question of when some work happened if you're following sane practices.

I do huge ETL projects that live or die on the accuracy of our timing data. Give me date(time)s in UTC and I'm happy. Anything else? Pain.

[msandin]

Of course we knew who did what and when, that was not the problem and I never said it was. But the start date+time they entered for recurring series was converted to UTC on the client before it was sent to the server. So when it was decided that what they really wanted wasn't to run it "every 24 hours after the start date+time" but to run it on the exact time they entered every day, starting on the day they entered, the information about the exact time they had entered was gone.", all we had was that time converted to UTC. This meant we could not deduce the original time zone in which it was entered and thus could not deduce which DST schedule it should follow to keep it running at the same time every day.

[msandin]

The answer to the question "when did some work happen" is an instant and I specifically said that instants should be stored in UTC. I'm talking about storing recurrent schedules, i.e. information about when an (potentially infinite) series of future events should take place. And that information is not a series of instants and can't be stored as UTC timestamps because it's potentially infinite, subject to future reconfiguration, subject to future timezone offset changes, and must be preserved in a format that allows it to be viewed and edited (Thursdays odd weeks at 10:00 is not easy to glean from a series of pre-calculated numbers).