There is a difference in relevance between online and local/physical events.
Having ONE time indicator is not enough to clearly tell a user when things are REALLY happening
Example 1: A webinar
Someone in the US plans a webinar at 9.00 AM Chicago time. A user in London will see that as 15.00 PM local time. So, during the event s/he will reserve time at 15.00 PM. All fine. This is how the system now works.
Example 2: An architect meet
Someone plan an architect meet in a local venue downtown Chicago from 9.00 AM to 12.00 AM. A person in London will see this as an event starting at 15.00 PM to 18.00 PM. S/he flies over because it is very important only to find that the meet was already finished.
I frequently have to caution people to check the real times. Right now it is very confusing.