To make it fair on people who can only attend one, maybe only the tickets from one of the events would count for people who attend both; whichever one they earned more in.Or tickets for people who only attended one could count twice. Either way sounds interesting.
For a bestest time of the day, I'm going with any time on a weekend. If specifics are needed, I'd say from 15:00 Saturday all the way to 05:00 Monday.