When I was a kid, there were no Teenage Mutant Ninja Turtles. There were plenty of mutant other things though. Every Saturday, there were black and white sci-fi thrillers about giant ants, shrinking men, and terrible accidents that made terrifying hybrids, like a man with a fly's head.
We take the calendar for granted. We all manage our lives hour by hour, day by day, week by week, but we seldom consider the truly strange thing that the measurement of time actually is. For example: do you know how Election Day is reckoned? How about knowing when Easter will occur, and why it will happen when it happens?
You know, the day isn’t even as long as you think it is; it’s shorter by four minutes. This adds up to a quarter day every year, or a whole day every four. More or less. Kind of. Maybe.
To reconcile this incongruity, every fourth year (except in certain centuries) is a Leap Year. Why a “leap” year? Well, because in common years, the advancement of the calendar puts fixed-date holidays on subsequent weekdays each year, i.e., Christmas is on Tuesday, then Wednesday the next year, then Thursday, etc. In leap years, Christmas would “leap” over Thursday to Friday.