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The Revised Julian Calendar

No calendar system is perfect. Even today's Gregorian calendar has flaws. But the Revised Julian calendar is a lot more accurate. How does it work, and why don't we use it?

Illustration image

Some Orthodox churches use the revised calendar.

The Revised Julian calendar is used by some Orthodox denominations, including the Orthodox Church in America.

©iStockphoto.com/Sibuet Benjamin

10 Times More Accurate

The Revised Julian calendar is one of the most accurate calendar systems ever developed. It reflects the length of the tropical year – the time Earth takes to complete a full orbit around the Sun – with an error of only 2 seconds per year.

Other calendar systems are much less accurate. Even the Gregorian calendar we use today has an error of 27 seconds per year.

How accurate are different calendars?

More Complex Leap Year Rules

The secret to its accuracy lies in the way it calculates leap years:

  • Years that are evenly divisible by 4 are leap years.
  • Exception: Years that are also evenly divisible by 100 and the remainder is neither 200 nor 600 when divided by 900 are not leap years.

Which years are leap years in the Gregorian calendar?

Why Don't We Use the Revised Julian Calendar?

First of all, it wouldn't make much of a difference. The offset between the Gregorian and Revised Julian calendars is negligible for many generations to come. The two systems will be in sync until the year 2800, which is a leap year in the Gregorian calendar but not in the Revised Julian calendar. In other words, February 29, 2800, in the Gregorian calendar will be March 1, 2800 in the Revised Julian calendar.

Gregorian calendar year 2800

However, the main reason why we do not use the Revised Julian calendar is that it was never meant to be a civil calendar. Rather, it was devised by Serbian scientist Milutin Milanković to reform time reckoning in the Orthodox Church. In 1923, the Greek Patriarch Meletius proposed its adoption. However, only a few national churches followed the directive, so most Orthodox denominations still observe the original Julian calendar.

Topics: Calendar, Timekeeping, Months

The Revised Julian Calendar
Used inSome Orthodox churches
Calendar typeSolar
Accuracy2 sec/year or
1 day in 31,250 years
Number of daysCommon year: 365
Leap year: 366
Number of months12
Correction mechanismLeap day


Calendars Worldwide

  1. Gregorian Calendar
  2. Julian Calendar
  3. Hindu Calendar
  4. Buddhist Calendar
  5. Islamic Calendar
  6. Jewish Calendar
  7. Persian Calendar
  8. Chinese Calendar
  9. Coptic Calendar
  10. Ethiopian Calendar
  11. Revised Julian Calendar
  12. Mayan Calendar

Calendar Servies

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