From Julian to Gregorian

There are many different ways to mark time and many different versions of calendars that are in use today. The most common calendar used today is the Gregorian. This calendar actually came about from a needed reform of the Julian calendar which was in use until the 1500’s. This change was caused because the Julian calendar had, while fixing many mistakes made previously, still been miscalculated for leap years.

When proposed by Julius Caesar in 46 BC, the Julian calendar had placed a leap year every four years because of the formula originally used. Because of this, the calendar gains a day every 128 years. The length of the Julian year had to be corrected as it had caused the calendar to drift about three days.

With the changes suggested by a doctor and astronomer from Italy, Aloysius Lilius, the Gregorian calendar was adopted during the papacy of Pope Gregory XIII in 1582. It took three hundred years for the Gregorian calendar to replace the Julian in most places.

While the Gregorian calendar is the most widely used calendar today, there are still many other calendars used including the Julian. The replacement of the Julian calendar happened because of the formula for the leap years but the Gregorian calendar is not entirely accurate either. However it is a bit closer, only being off one day every 3236 years, not every 128.