February soon became a month of rituals in order to ward off the bad omens from having even number of days. After a few years, the King Numa’s calendar was out of sync with the seasons. The Romans occasionally insert a 27 days leap month called Mercedoniaus. This new calendar caused so much confusion and headaches, that Caesar nixed the leap month and reformed the calendar again. By 46 BCE, Caesar aligned the calendar with the sun and added a few days to up to 365 but kept February 28 days long.
The leap year was introduced by Julius Caesar over two thousand years ago. There was only one rule: the leap year would be any year divisible by 4. This lead to too many leap years and wasn’t corrected until the introduction of the Gregorian calendar, in 1582, which allowed for realignment of the astronomical events like the solstices and equinoxes. The Gregorian calendar, named for Pope Gregory XIII has three rules for a year to be a leap year or not: 1) the year is evenly divisible by 4, 2) if the year is evenly divisible by 100, it is not a leap year, unless, 3) the year is evenly divisible by 400, then it is a leap year. So, the years 1900, 2100, and 2200 are not leap years but 1600, 2000, and 2400 are leap years.
Whew, confused? My head’s spinning a little bit. So, the adage that a leap year is every four year is not entirely accurate. So when someone asks you why February has 28 days and 29 days in a leap year, you could give them the long and confusing history behind the calendar’s development. Or you can simply say it is in accordance with astronomical events.