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.
You can also make and print a wall-style calendar.
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. 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 the month 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 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.
Despite these calendar reforms, each part of the Roman Empire 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. If you have been watching the news on television, 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).
AUC stands for anno urbis conditae. It was the year-numbering system in use by the Romans that was later superseded by AD or anno domini. (Actually there were several year-numbering systems in simultaneous use.)
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 mid 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. Ordinary folk were so confused by the change that they staged demonstrations against it.
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.