Julian Calendar

Julian Calendar

The Julian calendar was introduced by Julius Caesar in 46 BC. It was the predominant calendar in the Roman world and subsequently in most of Europe until the Gregorian calendar reform in 1582.

Gregorian Calendar Reform

In 1582, Pope Gregory XIII introduced the Gregorian calendar to correct the drift in the Julian calendar. The Julian calendar had an error of about 11 minutes per year, which accumulated to 10 days by 1582.

Key Differences

• Leap Years: Julian has leap year every 4 years. Gregorian excludes century years not divisible by 400.
• Accuracy: Gregorian is more accurate with only 26 seconds per year error vs 11 minutes for Julian.
• Date Difference: The gap between calendars increases by 3 days every 400 years.
• Current Difference: Julian calendar is currently 13 days behind Gregorian (as of 21st century).

Historical Usage

• Catholic countries adopted the Gregorian calendar in 1582
• Protestant countries adopted it gradually over the next centuries
• British Empire (including American colonies) adopted it in 1752
• Russia adopted it in 1918
• Some Eastern Orthodox churches still use Julian calendar for religious dates

Use Cases

• Historical research and genealogy
• Understanding old documents and dates
• Religious calendar calculations for Eastern Orthodox churches
• Academic and scholarly work