Dates of past events are always UTC, dates of future physical events must always be a timestamp and a location, dates of future virtual events are either UTC or location based depending on how virtual they actually are.
I can tell you from bitter experience that if you have an event where a person has to arrive at a place at a time and you store that as UTC instead of wall clock, you will have a problem at some point
I can tell you from bitter experience that if you have an event where a person has to arrive at a place at a time and you store that as UTC instead of wall clock, you will have a problem at some point