Initially, to make a proper transition from the Roman calendar (which had 355 days and which was basically a lunar calendar) to the Julian calendar, and to get the months and various feast days ...

Leap years were first introduced with the Julian calendar in 46 BC by Julius Caesar, who added an extra day to February every four years, based on the work of the astronomer Sosigenes, to account for ...

If the year can be evenly divided by 100, it is not a leap year unless the year is also evenly divisible by 400, according to mathisfun.com. For example, 2000 and 2400 are leap years, but 1800 ...

There are 52.143 weeks in a regular year and 52.286 in a leap year. ... The Julian calendar calculated the length of the year at 365.25 days, so it added an extra day every four years.

The solar calendar had the same number of days as the Julian calendar that was used in Europe in the same time period, but the Aztecs had a different method for subdividing the year. Their ...

Prior to the Gregorian and even Julian calendars, Roman King Numa Pompilius (715-673 BC) set about creating a calendar with equal-length months, the University of Chicago said.