Leap Year

Tomorrow will be February 29th, a day that only comes once every 4 years. Usually February only has 28 days but once every 4 years we add an extra day. Why do we do this? It is all because of how long it takes the Earth to orbit around the sun. Usually we think of a year as being 365 days long but in truth it takes us 365 days about about 6 hours to make one complete orbit. Every 4 years that extra 6 hours adds up to an extra day which gets added onto February. Why do we bother? Mainly it's because the Gregorian calendar was designed to keep the equinoxes, or days when there is a nearly equal amount of day and night time, around the same dates. If we didn't observe leap years the calendar would eventually be out of sync with the astronomical events that it is based on.