As many others have said, time and calendars is messy, and there is often no correct solution but just a bunch of trade-offs. Jon Skeets Storing UTC is not a Silver Bullet (https://codeblog.jonskeet.uk/2019/03/27/storing-utc-is-not-a...) was very influential for me in realizing some of the subtleties in what a point in time means for a user, and how that should incluece the design of a system.