Your brain doesn't use a man-made clock. It uses patterns.
In Audrey Niffenegger's novel The Time Traveler's Wife, Henry DeTamble is a man with a rare disorder that causes him to involuntarily travel through time. His wife Clare experiences life linearly, but never knows when or where she will see her husband next. "Each moment that I wait feels like a year," Clare says. "Through each moment I can see infinite moments lined up, waiting."
You don't need a time-traveling husband to have a warped experience of time like Clare's — think of how long a Monday back at work seems to stretch out, and how quickly the weekend flashes by. Time should march steadily, but that doesn't always match our perception. Neuroscientists and psychologists are searching for answers to this conundrum, using psychophysical experiments and brain scanning technology to unlock just how human brains track the passage of time. Researchers are gaining insights, and some of these findings could help us to better understand, among other things, disorders like schizophrenia and Parkinson's where sufferers have trouble perceiving time.
"Timing is fundamental, and it's involved in many different tasks," says John Wearden, a psychologist at the University of Keele in the U.K. "You wouldn't be able to tap on a keyboard or move your body unless you could program actions in time." Wearden has spent nearly 25 years researching timing in animals using the Scalar Expectancy Theory, which hypothesizes that animals have internal clocks. He was also the first person to apply this theory to human timing.
For the rest of the story: http://theweek.com/article/index/261814/unlocking-the-mystery-of-how-your-brain-keeps-time