The whole sequence of events in life can be seen as experiencing some kind of photo album, where every event is made up of certain inputs (what we see, what we hear, what we smell, etc.). If those inputs are stored in our brain in some kind of form along with the timelines, and if somehow we get access to it, then it opens up several interesting possibilities!
We would have seen photo albums of some of our past events like birthday party, wedding, wedding annviersary, etc. When we see those photos now, we might recognize the presence of certain people which we might have missed to see in the actual event! We might have even felt bad about the fact that they did not come for the event! Whereas now, when we see the photo, we get a different perspective. Similarly if we could somehow glance through the event album present in our brain, and if we can get back to past, we might be discovering certain things!