For past events, you can certainly store them as UTC and (possibly implied) location, provided that you also have a historically accurate database of all past time zone changes, so that you do not report that a meeting took place at 9:00 when it actually happened at 10:00, but the current time zone rules (at that location) are not the same today as they were on that date in the past.

For future events, you have to store them as location + timezone-naive dates and times, a.k.a. local time. Since if a meeting at a certain location is scheduled at 9:00, which is currently at 02:00 UTC, and then a timezone change happens, and UTC 2 suddenly means 10:00 at that same future date and location, the meeting will still happen at 9:00 local time. You cannot store future events as UTC only.