I'm a firm believer that time does fly when you're having fun or at least it flies when your attention is engaged.

Being out with friends and family and enjoying the evening is one theory we all know about. Seems we just we get to the meeting place and the evening is over. Awww, the beauty of being in the company of family and friends.

Studies have determined there are two kinds of time estimations when completing a task: prospective time estimation (estimator knows in advance he will be asked to make an estimate after the task is completed) and retrospective (estimator has been asked to provide a time estimate after the task is completed.) Our society is good with prospective estimates since most of us wear watches.

If you know in advance that you're going to have to estimate the time of a task & the task requires more attention, the faster time flies.