Leap Year + Bissextus: A Happy Coupling of Gregorian Figures

February 29th is that extra day added to the calendar every fourth year (except those evenly divisible by 400). To many, this brings up the word bissextus?  (I know, I know. It's 2016. Nobody cares anymore.)

Here's the skinny so you're in the know four years from now:

Bissext, or bissextus (Lat. bis, twice; sextus, sixth) is the day which is added to the Gregorian calendar every fourth year (except those evenly divisible by 100, unless they are divisible by 400) to compensate for the six hour difference in length between the common 365 day year and the actual length of the solar year. In modern usage, with the exception of ecclesiastical calendars, the intercalary day is added for convenience at the end of the month of February, as February 29, and years in which February has twenty-nine days are called "bissextile," or leap years.