The best estimation system I've seen is to actually BET on the completion date, closest gets a free lunch paid for by other members of the group.
Those dates were mostly informed guesses of what would actually happen or go wrong. Importantly this was between friends. Needless to say, they turned out very accurate.
Those dates were mostly informed guesses of what would actually happen or go wrong. Importantly this was between friends. Needless to say, they turned out very accurate.