Difference Between Julian & Gregorian Calendar


The calendar that is used worldwide today is called the Gregorian calendar, but it replaced an earlier calendar known as the Julian calendar. Although both calendars are Christian, many people are not aware of the differences between them. This article aims to highlight those differences.

Julian Calendar

The Julian calendar was introduced by Julius Caesar in 46 BC. This calendar was quite accurate but still had a small discrepancy that caused it to drift by almost a day every 128 years. By 1582 AD, the Julian calendar had drifted 10 full days from the actual date. To address this issue, Pope Gregory XIII introduced the Gregorian calendar in 1582, which gradually became adopted by Catholic countries around the world.

Gregorian Calendar

The Julian calendar had assumed a year to be 365.25 days, but later it was discovered that a solar year was actually 365.2422 and 365.2424 days in tropical and equinox years, respectively. This meant that the Julian calendar was off by 0.0078 and 0.0076 days, resulting in a difference of approximately 11.23 and 10.94 minutes, respectively. It became clear that the Julian calendar became inaccurate in calculating exact seasons and the date of Easter, which was significant for Christians. To address this issue, the Gregorian calendar was introduced in 1582 by Pope Gregory XIII. The reform of the calendar had been in progress since the time of Pope Paul III, and the suggestions of astronomer Clavius were considered when the Gregorian calendar was finally adopted by the Church.

Differences between Julian and Gregorian Calendar

– 10 days were omitted from the Julian calendar, and the day after October 4, 1582, became known as October 15, 1582, in the Gregorian calendar.
– In the Julian calendar, a leap year was any year divisible by 4. In the Gregorian calendar, a leap year is a year divisible by 4 but not by 100, unless it is divisible by 400.
– The Gregorian calendar introduced new rules for determining the date of Easter.
– In the Julian calendar, an extra day was added to a leap year before February 25. In the Gregorian calendar, the extra day is added after February 28.


1. The Gregorian calendar was introduced as a reform to the Julian calendar, which had drifted 10 days from the actual date by 1582.
2. The Julian calendar had an error of nearly a day every 131 years, making it inaccurate for calculating exact seasons and important Christian events like Easter.
3. The Gregorian calendar omitted 10 days from the Julian calendar and introduced new rules for determining leap years and the date of Easter.

Dmitri Ivanov
Dmitri Ivanovhttps://whats-different.com
Dmitri Ivanov, a writer and managing editor, was educated in Canada and holds a BS in Science. Dmitri loves doing research, writing, and teaching various courses.


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