I've been wondering for a while now but because of all the continuity errors in the new 52 timeline I have to ask. Who is responsible for the decision at DC to make it a 5 year timeline?
The 5 year timeline is just a chameleon timeline that changes all the time and will continue to change so just ignore yesterday's continuity and think only about today. Even in the year 2020, Superman will still have started 5 years ago, so just choose what history you like to cram into 5 years. You can even cram all the history from 1938 to present into a 5 year timeline if you really want to exercise your imagination. A 5 year timeline is just an arbitrary past since we know Superman did not start yesterday so we do have to say Superman started x years ago and Superman is still below 30 years of age right now since all the super heroes need to stay forever young.