I always took it as the number of new experiences you’re having. A work week might feel slower than a vacation week in the moment, but vacations tend to be more memorable. It’s shocking how much stuff you can pack into a few memorable days while months blur together.

There is research that shows that subjective passage of time depends on physiological changes to the brain. The most compelling example is that certain brain tumors make the passage of time seem extremely fast or slow to patients with them. The fact that time “seems to go faster” as you age is related to a normal aging related change (though natural, not caused by tumors.)