Tomorrow, February 29th, is a “leap day”, so remember to set your clocks back by 24 hours!  Fortunately, we don’t really have to do that.  Even clocks that keep track of the date as well as the hour pretty much all know when we have a leap year. But do you know WHY we have leap days?  Or exactly when?  Time is a surprisingly complicated topic, even when you ignore general relativity.  Hours, minutes, and seconds are essentially arbitrary units, so we can define them to fit our world however we want.  Days and years, on the other hand, are […]