Say you spend a long enough period of time (say a year) going through the same wake/sleep routine every day. You go to sleep around 11:00 pm (give or take 30 mins) and wake up in the morning at the same time using an alarm clock, say 7:00am. After a year you finally have a day where you can sleep in, and so you stay up a little longer and eventually fall asleep around 12am. Curiously, the next morning you still happen to wake up at exactly 7:00am with no alarm clock. Not 7:02, not 6:56, but 7:00 am on the nose. (This is something Ive personally experienced a number of times earlier when I was in school, and Im sure many of you have as well.) Right away, one may assume it is because our body is just used to sleeping for x hours as a daily routine, and so after those x hours of being asleep your mind/body is used to waking up. Except this still appears to happen regardless of what time you go to bed at. In the situation above, you were used to sleeping for about 8 hours every night for a year, and on your day off your body woke after about 7 hours, at the exact time you always woke up previously. So it seems that when we’re asleep our mind/body knows the time without having to look at a clock. Call it a “biological clock”, call it what you want, but is there an actual biological explanation for it? Is it just a coincidence that you’d wake at exactly 7:00am regardless of the time you went to bed at? On the flipside, when we’re awake (conscious life), we cannot tell the time accurately without looking at a clock directly. Of course we can estimate the time of day by looking at the sun or by some other external factors, but the point is we can never accurately know what time it is mentally, and yet in our subconscious we somehow do (or seem to). Is this clear evidence of time simply being a creation of our mind? To rule out the "it was just a coincidence" answer, Im wondering if anyone else had experienced this situation before and how often have you noticed it happen before. I also may be totally wrong about this, as I have no experience in the study of psychology and/or the conscious/subconscious mind. So if there's anyone with an educated background in this field who can shed some light, it would be much appreciated. Thanks.