What is a leap-year?
Contrary to popular belief, the earth does not take 365 days to revolve around the sun (translational motion), but actually takes about 365 days, 5 hours, 48 minutes and 45.10 seconds, so each year accumulates an equivalent of 1/4 of a day left over, so every 4 years we would have an additional time of approximately 23 hours and 50 minutes. This problem could cause to move the chronological time of the stations with the passage of the years. That is why to solve this problem was created the leap-year that consists of every 4 years a new day is added to the calendar at the end of February corresponding to the 29 of the same month. So every 4 years instead of having 365 days in the calendar, we have 366 days.