Can working backwards help you stay on schedule? Yes. But only if you do this...
When you're heading out to an event, the best way to plan out your schedule is to work backwards. If you have to be at the church for your wedding at 2pm, and the church is 20 minutes away, you really need to be on the road at 1:40. And if it's going to take you an hour to get into the clothes for the wedding, you need to start getting dressed at 12:40. But presumably you're going to shower beforehand, because let's face it, unless your intended spouse is blind and navigates by smell, your wedding day is probably the one day when you really want to smell nice. Assuming a 20-minute shower, you'll start getting ready at 12:20. Right?
WRONG! And here's why...
As any project manager knows, unexpected stuff goes wrong. Always. If you spend a few minutes brainstorming what could go wrong and add time into the schedule to correct for that, the universe simply adds more unexpected stuff. How much you plan doesn't matter; there will always be unexpected stuff.
So pad your schedule. And pad it in such a way that if you meet your estimates, you're left in a calm, cool, collected state.
If your event starts at 2pm and you plan to leave home at 1:40, back that up another 20 minutes and add a milestone called "ready to leave." You need to be ready to leave at 1:20. Then plan backwards from there, if possible, forgetting you even added the "ready to leave" milestone. Now you have a full extra 20 minutes to deal with unexpected stuff. This is different from trying to use a fake time ("let's pretend the wedding really starts at 1:40") because when you try to fool yourself, your brain fights back. Here, you're not fooling yourself, you're simply agreeing that "ready to go" is an important milestone you have to meet.
If unexpected stuff comes up, you'll have time to deal with it. But if nothing happens and you're on time, you'll have plenty of time to slam back a couple of shots of whiskey, because YOU'RE GETTING MARRIED - HOLY COW!