The circadian cycle that regulates sleep (amongst other things) has a 25-ish hour period for most people, in the absence of natural time signaling stimuli (i.e.

The circadian cycle that regulates sleep (amongst other things) has a 25-ish hour period for most people, in the absence of natural time signaling stimuli (i.e. sunlight and noise). In natural conditions, sunlight in the morning readjusts your body clock in roughly +/-15m increments. Recent research points to a faster way to adjust your body clock: http://news.ycombinator.com/item?id=199394 http://news.ycombinator.com/item?id=199394