A leap year is a year with an extra day added to the calendar — also known as leap day — on the29th day of February. The purpose is to keep it aligned with the Earth's orbit around the sun.

Leap years account for the inaccurate measure of time on the 365-day calendar. Technically it takes 365.242190 days for the Earth to orbit the Sun, according to the National Air and Space Museum.

The origin of the leap year, which adds one day—the 29th—to the end of February once every four years, dates all the way back to 46 B.C. An astronomer named Sosigenes of Alexandria told Julius ...

This year, Judaism's eight-day Festival of Lights begins at sundown on Wednesday, Dec. 25, aka Christmas Day. It's a rarity — the first time that particular holiday convergence has occurred in ...