1 PM UTC, for those looking for the one universal time reference.
But the real issue is why don't have browsers an integrated way of doing these computations by reading some HTML tags and also providing input widgets to make sure that it is universally readable by machines. Like <datetime ts="1700310507" ref-tz="Europe/Amsterdam" /> (if the event's timezone is Europe/Amsterdam, only for informational purposes)
SpaceX designed their page to display specific time zones for whatever reason.