Since it would be impractical for our calendars to add 0.24237 days at the end of each year, we make up the difference by adding an extra day, February 29, every fourth year, which is known as "leap year." Id. This would solve the problem entirely if a natural year were actually 365.25 days. However, because the actual figure is slightly less at 365.24237 days, adding a full day every four years ends up overcompensating. Id. To correct this, the Gregorian calendar approximates the natural year at 365.2425 days. See Leap Years, Naval Oceanography Portal, http://www.usno.navy.mil/USNO/astronomical-applications/astronomical-information-center/leap-years (last visited June 4, 2011).