Julian Calendar
The ancient Roman calendar introduced by Julius Caesar, still used by Orthodox churches
About the Julian Calendar
The Julian calendar was introduced by Julius Caesar in 45 BCE as a reform of the Roman calendar. It was the predominant calendar in the Roman world and subsequently most of the Western world for more than 1,600 years. Today, it is still used by several Eastern Orthodox churches to calculate fixed religious holidays.
📅 Key Features
- 365.25 days per year - Average year length with leap years
- Leap Year Every 4 Years - Simple rule: divisible by 4 = leap year
- 12 Months - Same month structure as Gregorian calendar
- 13-day offset - Currently 13 days behind Gregorian calendar (in 21st century)
- Still in Religious Use - Orthodox churches use it for feast days
🏛️ Historical Development
Julius Caesar, with the help of the Alexandrian astronomer Sosigenes, introduced this calendar to replace the old Roman calendar which had become severely misaligned with the seasons. The Julian calendar established the 365-day year with a leap day every four years, bringing the calendar year much closer to the solar year. The month of July was named in Caesar's honor.
⛪ Orthodox Christian Holidays (Old Calendar)
- January 7 - Christmas (13 days after Gregorian Dec 25)
- January 19 - Theophany/Epiphany
- April (varies) - Orthodox Easter (calculated using Julian calendar)
- June (varies) - Pentecost (50 days after Easter)
- August 19 - Transfiguration of Jesus
- September 14 - Exaltation of the Holy Cross
🔄 Gregorian Reform
By the 16th century, the Julian calendar had drifted 10 days from the solar year due to its leap year rule being slightly too generous (365.25 days vs actual solar year of 365.2422 days). Pope Gregory XIII introduced the Gregorian calendar in 1582, which refined the leap year rule and removed 10 days to realign with the seasons. Different countries adopted the Gregorian calendar at different times over the following centuries.
📊 Why the Julian Calendar Drifts
The Julian calendar assumes a year is exactly 365.25 days long (365 days + 1 leap day every 4 years). However, the actual solar year is approximately 365.2422 days. This 11-minute difference accumulates to one full day every 128 years, causing the calendar to slowly drift relative to the seasons.
🌍 Current Usage
While most of the world has adopted the Gregorian calendar for civil purposes, several Eastern Orthodox churches (including Russian, Serbian, Georgian, and Jerusalem patriarchates) continue to use the Julian calendar for calculating the dates of religious holidays. Some Orthodox churches have adopted the Revised Julian calendar, which is more accurate than the Gregorian calendar.