"The more detailed the memory, the longer the moment seems to last. This explains why we think that time speeds up when we grow older. Childhood summers seem to go on forever, while old age slips by while we're dozing. The more familiar the world becomes, the less information your brain writes down, and the more quickly time seems to pass.
Time is this rubbery thing. It stretches out when you really turn your brain resources on, and when you say, 'Oh, I got this, everything is as expected,' it shrinks up."
- David Eagleman