What is a leap year and why do we need them?
A single orbit of the Sun lasts approximately 365.25 days, which adds up to an additional day every four years.
The extra leap day falls on February 29, which was adopted almost 2,000 years ago by the Roman dictator Julius Caesar in the year 46 BC.
If the Gregorian Calendar did not take into account the extra day every four years, it would differ greatly from the solar calendar.
Every four years, the calendar would be off by a single day.
Every 100 years, the calendar would be off by 25 days and so on.