When looking back on the last operation I had, I remembered the strange feeling of being awake one minute on the operation table and giggling as the anesthesia kicked in, then waking up in a completely different room, with a tube down my throat. I had no idea wether I had been unconcious for hours or minutes. I had no sense of time at all. There is something about being unconsious that strips humans of our sense of time. When our minds are functioning we can feel time passing and see it happening around us. But when our minds are shut off, wether it be by chemical influence such as anesthesia, or during the early stages of a very deep sleep we have no sense of time at all. This begs the question, is time ONLY in our heads?
Maybe time is in our heads after all and the only reason that time exists is because humans are here to measure it!