You have to make the distinction between absolute time and relative time. You use relative time for appointments/calendars and any other kind of "people oriente

You have to make the distinction between absolute time and relative time. You use relative time for appointments/calendars and any other kind of "people oriented" time. Absolute time is everything else. Relative time is a sticky mess. I think The Doctor referred to it as wibbly wobby timey wimey stuff -- and it really is. Just store this crap as a string along with the user's location. Don't bother storing the timezone, because DST changes every other day and some retard or another is always adding/removing timezones. When it comes to appointments and the like, you only ever have to bother with conversions when sharing it with users in a different location/timezone. That's when you perform the relevant magic. Not before. Not ever. When it comes to absolute time, things are lot easier. Use UTC. Always. No exceptions. 'nuff said.