I listened to a recent discussion on NPR (forget which program) which drew a distinction between the perception of time as it passes and the perception of time

I listened to a recent discussion on NPR (forget which program) which drew a distinction between the perception of time as it passes and the perception of time looking back. For example, after a year of doing the same thing over and over, you can look back and wonder where all the time went (even though it felt like it took an eternity while you were experiencing it). Whereas after a year of doing interesting/different things, the time may seem to pass quicker, but thinking back on the year, time seems to have passed much more slowly because there are more markers in your memory.