You might have assumed “Time flies when you’re having fun” simply means that you’re less likely to keep an eye on the clock when you’re being entertained. But the phenomenon could actually have a scientific explanation. According to one theory, increased dopamine production in your brain—which happens when you experience pleasure—may slow down your body’s internal clock, making you feel like time is moving more slowly than it really is.

In that case, we’re hoping this episode of The List Show slows your internal clock to a near standstill. Mental Floss editor-in-chief Erin McCarthy is talking all things time, from leap days (and leap seconds) to Sandford Fleming’s failed attempt at making “Cosmic Time” a thing. And while you might picture time progressing from left to right, not everybody does: People who read from right to left often conceptualize time as moving that way, too, and some others even perceive the past to be in front of them.

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