Every four years, an extra day is added to the calendar, But even with leap day, the math doesn't exactly, well, math.

This year is a leap year, meaning Feb. 29 was added as the 366th day on the calendar. Here's what to know about its meaning, ...

4 Leap years were introduced by the Roman emperor Julius Caesar, who created a new calendar to take the extra quarter-days into account. The Julian calendar ... the exact date on which this ...

He introduced his Julian calendar in 46 BCE. It was purely solar and counted a year at ... t have that date built in. There are about 5 million people worldwide who share the leap birthday out ...

Prior to the Gregorian and even Julian calendars ... emperor adopted a 365-day calendar and added 10 days the calendar, including a leap day in February every four years, calendar.com said.