We stored and transmitted exclusively UTC, which put the burden on the UI at display time (trivial) and backend business logic (complex, but simplified with rob

We stored and transmitted exclusively UTC, which put the burden on the UI at display time (trivial) and backend business logic (complex, but simplified with robust utility functions that everyone understood well) in accounting for timezones when material. We only had a dozen issues due to it so I believe it worked pretty well compared to the war stories I heard from comparable companies in the fintech space.