Julian vs Gregorian Calendar
The device that we make use of to answer the age old question of what date is it is known as a calendar. The calendar that is used the world over today is known as the Christian calendar or the Gregorian calendar. This calendar system took over from the earlier Julian calendar that was in use since 45 BC till 1582. Though both are Christian calendars, many people do not know the differences between the two western calendars. This article attempts to highlight these differences.
This is a calendar that was introduced to the world by Julius Cesar in 46 BC. This was a calendar that as remarkably close to the actual length of a year but it was found that it left over close to a day in a period of 128 years. So by the time it was 1582 AD, the Julian calendar had actually drifted 10 full days from the actual date. To reform the calendar, Pope Gregory XIII introduced Gregorian calendar in 1582 that was slowly and gradually adopted by catholic countries around the world.
When Julius Caesar won Egypt in 48 BC, he felt the need of calendar reform. The calendar he introduced divided a year into 12 months and contained 365 days with an extra day every fourth year to take into account the actual length of 365.25 days for a solar year.
The length of a year as 365.25 taken in Julian calendar was later proved to be wrong as a solar year was found to be 365.2422 and 365.2424 days in tropical and equinox years. This meant that Julian calendar erred by 0.0078 days and 0.0076 days in the two cases. This amounted to a difference of 11.23 minutes and 10.94 minutes respectively. The error meant that Julian calendar missed out nearly a day in every 131 years. After many centuries, Julain calendar became inaccurate to calculate exact seasons and the most important day for the Christians, the Easter. To reform Julian calendar, Gregorian calendar was introduced in 1582 by Pope Gregory XIII. However, work on the reform of calendar started in the time of Pope Paul III, and suggestions of the famous astronomer Clavius were taken into consideration when finally Gregorian calendar was adopted by the Church.
What is the difference between Julian and Gregorian Calendar?
• 10 days were omitted from the Julian calendar, and the day following October 4, the day on which Gregorian calendar was adopted, was known as October 15, 1582.
• While in Julian calendar, a leap year was an year that was divisible by 4, it was declared that a leap year could be an year divisible by 4 but not by 100 or an year divisible by 400.
• Gregorian calendar introduced new laws to determine the date of Easter.
• While the day before February 25 was chosen to add an extra day in a leap year in Julian calendar, it was taken as the day after 28th February in the Gregorian calendar.