You need DST rules to handle future calendar entries correctly. Current network time doesn't help you with that. Example: you have a calendar entry that is def

You need DST rules to handle future calendar entries correctly. Current network time doesn't help you with that. Example: you have a calendar entry that is defined to happen in November 1, 2016, 10:00am Helsinki time. To show that in US Eastern time zone you need to know the DST rule of both. If the calendar entry start would be defined in UTC, you would still need DST rule of US Eastern to show it correctly.