Happy Leap Day!
Sincerely. Happy Leap Day! If you know me at all, you might think I am being disingenuous, sarcastic, or hypocritical by saying this. Not at all. Leap Day is the only day in popular culture that is an acknowledgement of our intellectual progress rather than of our stupidity. It is the only day that, while arbitrarily placed, does not exist arbitrarily.
The Earth rotates on its axis once a day, and travels around the Sun once every 365.256366 days. A year does not divide evenly into days. Therefore, if we held to a firm 365 days in a "human" year, our seasons would flip about every 700 years. To keep things stable, we insert an extra day every 4 years. But because the fractional portion is slightly larger than 0.25, we need to remove a few leap days once in a while. Every 400 years, we remove 3 leap days. 1700, 1800, and 1900 did not have leap days, and 2100, 2200, and 2300 will not. 1600 and 2000 did.
As humans, we have known about the day/year problem for thousands of years. How many people today do you think could explain the meaning of February 29th?