It looks like in the recent event updates, Past events get their dates and times locked. I couldn’t find a way to reschedule a Past event via Control. 

Vote for this idea if you’d like to be able to do that!

However, you can do it via the API (and because it’s possible that way, I wouldn’t anticipate this Idea will be a high priority). 

Use the Reschedule Event API operation and it will successfully update the dates and times. Then, assuming your event is now in the future, the event will change back to a published event.