This is from an interesting interview with the neuroscientist David Eagleman, who specialises in the way our brains process time:
We all go through life assuming that time is an external river that flows past us. But experiments in my laboratory over the past decade have shown that this is not precisely the case. Time is an active construction of the brain. We can set up simple experiments to make you believe that a flashed image lasted longer or shorter than it actually did, or that a burst of light happened before you pressed a button (even though you actually caused it with the button), or that a sound is beeping at a faster or slower rate than it actually is, and so on. Time is a rubbery thing.
Link to interview.
(Annoyingly, Eagleman is also an excellent writer: his book of short stories about the afterlife, Sum, is mindblowingly good.)