60 seconds per minute.
60 minutes per hour.
24 hours per day.
365.242216 days per year.

A year is based on the time it takes the earth to orbit around the Sun. But since that takes 365.242216 days, Mr Gregorian Calendar decided to round a year down to 365 days, save all those 0.242216 days as retainer and hand them out as an one-day-bonus to all his followers every four years. That bonus is the 29th of February, and today is one of those days.

So congratulations to all Mr Gregorian Calender followers.
Today is a day you work for free.