This page contains information about the three calendars that are in use in Christendom:
You can go to another page to generate a list of holy days in the year you specify. If you are wondering when Easter Day falls in a given year, this is how to find out.
- Western Holy Days
Valid for the years 1900 to 2099, inclusive.
- Eastern Holy Days
Valid after 325, also finds Easter for all locations before 1583 and in English-speaking countries before 1753.
The Julian Calendar
In the year 3961 AM, which we call 46 BC, Julius Caesar standardized the civil calendar of the Roman Empire so that it had twelve months with fixed lengths. Before then, the date depended on observations of the sun and the moon, as determined by pagan priests who were given that task. He also introduced the concept of the leap day, which adds a day to February every four years. The Roman government used the Julian Calendar for official purposes during the events of the New Testament, but the general population continued to use their own local calendars. The month of Quintilis was renamed
July to honor him for this calendar reform.
Later, Caesar Augustus made a minor calendar reform. Under Julius Caesar’s calendar, leap day came in the middle of February and had the same date as the day before. Caesar Augustus moved the leap day to the end of the month and gave it its own date. February was an unpopular month, because it contained an unpleasant pagan religious observance, so he moved one day from February to the month of Sextilis, which was renamed
August in his honor. However, the resulting calendar is still called the Julian calendar.
The calendar resulting from these reforms was the official government calendar of the Roman Empire, but for day-to-day purposes on the local level, each area continued to use its own local calendar. To avoid confusion, documents intended for wide distribution often dated events by referring to the names of officials who were in office rather than by using a calendar date. The New Testament reflects this practice. Eventually the Church had to devise a method of determining the date of Easter that would work everywhere in the Roman Empire. It used the Julian Calendar for this purpose, because even though people preferred to use their local calendars, they could easily determine the date in the Julian Calendar no matter where they were.
All Orthodox churches continue to use the Julian Calendar when they calculate the date of Easter and holy days that are dependent on the date of Easter. Some Orthodox churches still use the Julian Calendar for all holy days, such as the Orthodox Churches of Jerusalem, Georgia, Russia, and Serbia and the other Slavic churches. You may have noticed that Christmas was celebrated on 7 January in Serbia and Russia. That is because the Serbian Orthodox Church and the Russian Orthodox Church use the Julian Calendar for all holy days. Currently, Julian 25 December falls on Gregorian 7 January.
In computer technology, the term julian date does not refer to the Julian Calendar. It is a misnomer for a method of ignoring the months and numbering the days of the year consecutively from 1 to 365 (or 366).
There were several year-numbering systems. One was AUC, which stood for
anno urbis conditae or
since the founding of Rome, another was AM, which stood for
anno mundi or
year or the world, according to which Jesus was born in the year 5500. Other systems were in use, such as naming the current consuls or, in the east, counting the years since Diocletian. In the sixth century, Dionysius Exiguus invented our current Anno Domini system, but it took about 200 years to come into common use—however, the year number was used by the government and the church, and ordinary people weren’t aware of it or didn’t care.
If we still were still using the AM year-numbering system, today’s date would be something like 13 July 7516!
The Gregorian Calendar
By the sixteenth century, it became obvious that the Julian Calendar was out of step with the seasons, causing Easter to slip later and later in the year. In 1582, Pope Gregory revised the Julian Calendar to fix this problem, and the result is the Gregorian Calendar that we all use for civil purposes. (Fortunately, no one named a month after him, so there is no month of Greguary.) The Western churches and the Orthodox Church of Finland use the Gregorian Calendar to calculate all holy days. The Gregorian Calendar is identical to the Julian Calendar, except for the following:
- Ten days were removed from October 1582. This put the equinoxes back on the proper dates.
- In century years not divisible by 400, February does not receive an extra day.
- Thus there was a 29 February 1900 in the Julian Calendar, but not in the Gregorian Calendar. This ensures that the Gregorian Calendar remains synchronized with the seasons for the next 10,000 years or so—without this change, Easter would fall in the summer time after the 100th century. However, this causes the difference between the calendars to increase with time. At present, the Julian Calendar is 13 days slow compared to the Gregorian Calendar.
- New Year’s Day was moved from March to 1 January.
The British Empire—which at the time included what is now the United States—switched to the Gregorian Calendar in September 1752.
The Revised Julian Calendar
Orthodox churches agree in principle that a calendar reform is highly desirable, but they deny that Pope Gregory had the authority to do it. They hold that only an Ecumenical Council can undertake an ecclesiastical calendar reform that affects the date of Easter. However, some Orthodox churches have adopted the Revised Julian Calendar, which coincides with the Gregorian Calendar for at least the next 8,000 years. They use the Revised Julian Calendar only for holy days that are not in the Easter cycle.