The Julian Calendar was introduced by Julius Caesar in 45 BCE. Some Eastern Orthodox churches retain it for fixed feasts, an approach called the “Old Calendar.” In the Gregorian calendar used in the United States, their Nativity of Christ falls on January 7 rather than December 25.
What is the Julian Calendar?
It has 365 ordinary days and adds a leap day every four years, so its average year is 365.25 days. Because that rule differs from the Gregorian calendar, the dates drift apart over centuries. The Gregorian reform of 1582 corrected the drift by omitting selected days and adopting more precise leap-year rules.
Between 2001 and 2099, the Julian calendar is 13 days behind the Gregorian calendar used in the United States. “Old” describes its place in church tradition, not its suitability for daily life.
Why do some Orthodox churches keep the “Old Calendar”?
For Eastern Orthodox Christians, the calendar is part of an inherited pattern of worship, fasting, and commemoration. Some jurisdictions and independent communities preserve Julian dates for fixed feasts; this practice is commonly called the Old Calendar, and its adherents are sometimes called Old Calendarists. The choice expresses continuity with tradition and, for some congregations, ethnic or cultural identity.
Keeping the Julian calendar does not mean these churches reject the Gregorian calendar or teach a different date for Christ’s birth; they use it for civic life. Many Orthodox churches use a Revised Julian Calendar for fixed feasts and are often called New Calendar churches. In North America, Greek Orthodox and Orthodox Church in America congregations generally use it for fixed feasts; some Antiochian Orthodox and Russian Orthodox Church Outside Russia congregations retain Julian dates. Its fixed-feast dates match Gregorian between 2001 and 2099, although churches may still calculate Pascha with Julian tables.
How are Christmas and other holy days shifted?
From 2001 through 2099, December 25 in the Julian calendar falls on January 7 in Gregorian dating. Thus an Old Calendar church celebrates the Nativity of Christ on January 7, while churches using Gregorian or Revised Julian dates generally celebrate on December 25. The feast may be called Christmas or the Nativity.
Other fixed observances—those assigned the same date each year—shift by 13 days. For example, Theophany, observed on January 6 in the Julian calendar, falls on January 19 in Gregorian dating. The Nativity Fast and many saints’ commemorations also follow the church’s chosen calendar.
Pascha, the Orthodox Easter, is calculated from lunar and solar rules rather than fixed to a date. Old Calendar churches using the Julian paschal calculation observe it on the same date as, or later than, Easter in Western Christian churches. The liturgical calendar explains these distinctions.
What should you expect at an Old Calendar service?
Expect an Orthodox Divine Liturgy with the congregation’s usual prayers, hymns, icons, processions, and clergy. The calendar affects when observances occur, not the basic form of worship. Check the parish’s published schedule: an Old Calendar Nativity service will be listed on January 7, even though the service itself is Christmas.
If you are new, the first-time church guide explains general customs. Orthodox services often include standing, kneeling or bowing, and incense; follow the congregation and the guidance of those greeting you.