Julian Calender

The Julian calendar was introduced by Julius Caesar in 45 BCE and replaced the Roman calendar, which was a very complicated lunar calendar, based on the moon phases. It required a group of people to decide when days should be added or removed in order to keep the calendar in sync with the astronomical seasons, marked by equinoxes and solstices. In order to create a more standardized calendar, Julius Caesar consulted an Alexandrian astronomer named Sosigenes and created a more regulated civil calendar, a solar calendar based entirely on Earth's revolutions around the Sun, also called a tropical year. It takes our planet on average, approximately 365 days, 5 hours, 48 minutes and 45 seconds (365.242189 days) to complete one full orbit around the Sun. A common year in the Julian calendar has 365 days divided into 12 months. In the Julian calendar, every four years is a leap year, with a leap day added to the month of February.