I work on a Calendar product and I can assure you that working with dates, times, and timezones is a complex endeavor. We just fixed a bug in a legacy part of

I work on a Calendar product and I can assure you that working with dates, times, and timezones is a complex endeavor. We just fixed a bug in a legacy part of the application where timezones were converted properly when accepting an event from an ICS file but on export through our CalDav server, certain timezones (ones unknown by name to the OS) weren't converted properly so we were providing the wrong start time to the event. It's too bad Microsoft uses different names for timezones than basically everyone else.