Revised Julian calendar

The Revised Julian calendar, also called the new calendar or the Milanković calendar, was created in 1923 by the Serbian scientist Milutin Milanković. He wanted to make a better calendar to help match dates used by different churches and nations.

At that time, the Eastern Orthodox Church and its nations used the older Julian calendar. Catholic and Protestant nations used the Gregorian calendar, introduced by Pope Gregory XIII's papal bull Inter gravissimas in 1582.

The Revised Julian calendar matches the Gregorian calendar from March 1, 1600, until February 28, 2800. Many Eastern Orthodox churches now use this calendar for their religious events. These include the Ecumenical Patriarchate of Constantinople, the Albanian Orthodox Church, the Greek Orthodox Patriarchate of Alexandria, the Greek Orthodox Patriarchate of Antioch, the Bulgarian Orthodox Church, the Romanian Orthodox Church, the Cypriot Orthodox Church, the Church of Greece, the Orthodox Church of the Czech Lands and Slovakia, the Orthodox Church of Ukraine, and the Orthodox Church in America. However, some churches, like the Russian Orthodox Church and the Serbian Orthodox Church, still use the Julian calendar.

The Revised Julian calendar works much like the Gregorian calendar. It has the same months and days, but there is a special rule for leap years. Years divisible by 100 are usually not leap years, except when they leave a remainder of 200 or 600 when divided by 900. This means years like 2000 and 2400 are leap years, just as in the Gregorian calendar.

Background

In the history of Christianity, some groups started using a new calendar in 1582. That year, the Catholic Church changed from the old Julian calendar to the new Gregorian calendar.

By the 1700s, many Protestant countries began using the Gregorian calendar. In the Kingdom of Great Britain, they started using it in 1752. Some Eastern Catholic Churches also talked about changing. They wanted to keep their special traditions the same. The leaders agreed to respect these traditions.

Implementation

Some people in Greece wanted to change how they counted days. They started using the Gregorian calendar for regular life on February 16, 1923.

The leader of the Orthodox Church asked other Orthodox churches to use this new way too. Many agreed. They moved forward by thirteen days, so October 1 became October 14. They also made new rules for leap years. This made their calendar very similar to the Gregorian calendar.

Arithmetic

The Revised Julian calendar and the Gregorian calendar are the same from March 1, 1600, to February 28, 2800. After that, the two calendars differ by one day. For example, March 1, 2800, in the Revised Julian calendar is February 29, 2800, in the Gregorian calendar.

The Revised Julian calendar has a few fewer leap days than the Gregorian calendar. This makes the Revised Julian calendar a little shorter than the Gregorian calendar. On average, the Revised Julian calendar is about 24 seconds shorter each year than the Gregorian calendar. Over many years, this small difference adds up.

March equinox

This section shows a chart of when the spring equinox happens each year. The chart was made using special computer tools that find the exact moments when the sun's position changes to mark the start of spring.

The chart looks at dates up until the year 4400. It shows that the Revised Julian calendar keeps the spring equinox in about the same place over many years, which is good. There are small changes over time—about two days—because the way leap years are added isn't perfectly smooth. But these small changes don't matter for practical use or special events.

Adoption

In 1923, a new way to keep track of dates called the Revised Julian calendar was created. Many Eastern Orthodox Churches decided to use parts of this new calendar for important holy days, like Christmas.

Some churches started using the new calendar at different times. For example, churches in Constantinople, Cyprus, and Greece began using it in March 1924. Others, like the Romanian Orthodox Church, followed in October 1924. By 2023, eleven churches were using the Revised Julian calendar, but some still use the older way.

Defense

The Revised Julian calendar was made to fix problems with the older Julian calendar. Over time, the old calendar made important dates move to the wrong seasons. For example, December, which should be cold, would become warm. This made it hard for churches to celebrate events like Christmas on the right dates. The new calendar helps keep these special days aligned with the right times of the year.

Criticism

Some people think changing the calendar was not needed. They believe there were no strong religious reasons for the change, only social ones. The idea to change the calendar was suggested by Meletios Metaxakis, the Ecumenical Patriarch of Constantinople, though his position was debated by some.

Others argue that because the Julian calendar was used when an important meeting happened long ago to decide when Easter should be celebrated, only a big meeting of leaders should decide to change it. They feel that using different calendars in different places has caused Eastern Orthodox churches to not celebrate Easter together on the same day anymore. This breaks the unity that was decided at that meeting long ago.