Well, that depends. If I needn't to know the exact date, but rather the event, I would go to the closest thing in history to an actual Zep Tepi, just to see if all these traditions of a highly sophisticated and spiritual antediluvian society are true or not.
If I needed to know the date, I would go to A.D. 2030 or thereabouts to talk to myself and see if I made any crucial errors that I might want to avoid..
