Hmm. If I could redo a day, I'd redo June 6th, 2008. It really messed with my whole entire life. Like, I'd have to start at midnightish because I made a horrible mistake that messed up my whole life for a good 5 months, and there are still horrible ramifications to that decision that I made in the middle of the night to this day.
Good days are meant to stay frozen in time, and not to be relived. I like thinking I can make any day as good as the days of my past.