The Church Calendar

The Orthodox Church uses multiple interlocking calendrical systems: the Julian Calendar for fixed feasts (in ROCOR and the Moscow Patriarchate), the Paschalion for calculating the date of Pascha, and the liturgical cycles of the Octoechos, Triodion, and Pentecostarion for organizing worship throughout the year. The liturgical year begins on September 1 (Old Style), the day of the Church New Year or Indiction.

Tradition: Russian Orthodox / ROCOR (with notes on pan-Orthodox and New Calendar practices)

The Julian Calendar

History

The Julian Calendar was introduced by Julius Caesar in 46 BC and was the civil calendar of the Roman Empire and, subsequently, of Christendom. It operates on a year of 365.25 days (with a leap year every four years). The actual solar year is approximately 365.2422 days, producing a discrepancy of about one day every 128 years.

By the 16th century, the Julian Calendar had drifted approximately 10 days behind the solar year. In 1582, Pope Gregory XIII introduced the Gregorian Calendar, which corrected the drift and added a more precise leap-year rule (century years are leap years only if divisible by 400). The Gregorian Calendar was gradually adopted by Western nations but rejected by the Orthodox world.

The Current Difference

In the 20th and 21st centuries (from March 1900 through February 2100), the Julian Calendar is 13 days behind the Gregorian Calendar. Thus:

Christmas (December 25 OS) = January 7 NS
Theophany (January 6 OS) = January 19 NS
The Church New Year (September 1 OS) = September 14 NS

The abbreviations OS (Old Style) and NS (New Style) are used throughout this guide.

Who Uses the Julian Calendar

The Julian Calendar for all fixed feasts is used by:

The Russian Orthodox Church (Moscow Patriarchate)
ROCOR (Russian Orthodox Church Outside Russia)
The Serbian Orthodox Church
The Georgian Orthodox Church
The Church of Jerusalem
Mount Athos

The Revised Julian Calendar (New Calendar)

In 1923, an inter-Orthodox congress in Constantinople proposed the Revised Julian Calendar (sometimes incorrectly called the “New Julian Calendar”), devised by the Serbian scientist Milutin Milankovic. This calendar aligns with the Gregorian Calendar for fixed feasts (using a more astronomically precise leap-year formula) but retains the traditional Paschalion for calculating Pascha. Thus, New Calendar churches celebrate Christmas on December 25 (the same day as the West) but Pascha on the same date as Old Calendar churches.

Churches using the Revised Julian Calendar include:

The Ecumenical Patriarchate of Constantinople
The Greek Orthodox Church
The Romanian Orthodox Church
The Bulgarian Orthodox Church
The Orthodox Church of Alexandria
The Antiochian Orthodox Church (the Patriarchate of Antioch initially rejected the 1923 proposal but subsequently adopted the New Calendar for fixed feasts; the standard accounts date the change to the 1940s)
The Orthodox Church in America (OCA) – uses the Revised Julian Calendar for fixed feasts (with some parishes and the Diocese of Alaska remaining on the Julian Calendar)

ROCOR’s Position: ROCOR has consistently rejected the Revised Julian Calendar as an unwarranted innovation adopted without pan-Orthodox consensus. The calendar question has been a significant point of tension in inter-Orthodox relations. ROCOR views the adoption of the New Calendar as a concession to Western influence and a departure from the received tradition. The 1923 congress that proposed the change was not a properly constituted Ecumenical or Pan-Orthodox Council (Schmemann, Introduction to Liturgical Theology; various ROCOR synodal statements).

Practical Consequences of the Calendar Difference

The calendar difference creates a pastoral challenge for Orthodox Christians living in Western societies:

ROCOR and Moscow Patriarchate faithful celebrate Christmas on January 7 NS, two weeks after the Western Christmas.
The Nativity Fast (ending December 24 OS / January 6 NS) extends through the entire Western Christmas and New Year season.
The feast of Theophany (January 6 OS / January 19 NS) falls after the Western Epiphany.
Some families with members in different jurisdictions face the difficulty of celebrating the same feasts on different dates.

The Paschalion: Calculation of Pascha

The Three Rules

The date of Pascha (Easter) is determined by the Paschalion. [Corrected: this article previously described the Paschalion as "the system of calculation established by the First Ecumenical Council (Nicaea, 325)." Nicaea settled the *principles* — that Pascha is kept on a Sunday, uniformly throughout the Church, and independently of the Jewish reckoning — but did not promulgate the computus later attributed to it; the Alexandrian computus was received gradually after the council, and Churches kept differing Paschal dates for some three centuries afterwards. The point is made correctly in this article's own rule 2 below. See [How Pascha Is Reckoned](../../liturgical-time-and-the-calendar/03-the-paschalion/how-pascha-is-reckoned.md) and [Nicaea and the Independence of the Christian Reckoning](../../liturgical-time-and-the-calendar/03-the-paschalion/nicaea-and-the-independence-of-the-christian-reckoning.md).] The traditional rules, as they were received, are:

Pascha must fall after the vernal (spring) equinox. The Alexandrian computus received by the Church after Nicaea fixed the equinox at March 21 (Julian). Because the Julian Calendar has drifted, the Julian March 21 now corresponds to April 3 in the Gregorian Calendar, which is well after the astronomical equinox (approximately March 20-21 Gregorian).
Pascha must fall on the Sunday after the paschal full moon – the first full moon on or after the equinox, as calculated by the Church’s own (Alexandrian) lunar tables, not by astronomical observation or by the Jewish calendar. The popular formulation that Pascha “must fall after the Jewish Passover” is not among the original rules: the Council of Nicaea decreed precisely that the Christian Pascha be computed independently of the Jewish reckoning. The “after Passover” requirement first appears as a formal principle in the 12th-century canonist John Zonaras’s commentary on Apostolic Canon 7 (hence the scholarly name “Zonaras proviso”), and in practice Orthodox Pascha does follow Passover – but as a byproduct of the aging Julian lunar tables, not as a rule of the Paschalion (Patsavos, “Dating Pascha in the Orthodox Church,” Greek Orthodox Archdiocese; Kuzenkov, Khristianskie khronologicheskie sistemy).
Pascha must fall on a Sunday – the day of the Resurrection.

In practice, Orthodox Pascha is calculated using the 19-year Metonic cycle of lunar tables as received in the Alexandrian tradition, applied to the Julian Calendar. Because the Julian equinox and the Julian lunar tables both diverge from astronomical reality, Orthodox Pascha can fall:

On the same date as Western Easter (occasionally)
One week after Western Easter
Four weeks after Western Easter
Five weeks after Western Easter

The dates never differ by two or three weeks. The maximum difference is five weeks; the minimum (when not coinciding) is one week.

All Orthodox churches – both Old Calendar and New Calendar – celebrate Pascha on the same date, using the same Paschalion. This is one of the few points of universal Orthodox agreement on the calendar question.

The Paschal Cycle

The date of Pascha determines the dates of all the moveable feasts:

Meatfare Sunday: 56 days before Pascha (the Sunday before the start of the Triodion fast)
Cheesefare Sunday (Forgiveness Sunday): 49 days before Pascha (the Sunday before Great Lent)
Great Lent begins: Clean Monday, 48 days before Pascha
Lazarus Saturday: 8 days before Pascha
Palm Sunday: 7 days before Pascha
Holy Week: Monday through Saturday before Pascha
Pascha: The Feast of Feasts
Bright Week: The week after Pascha
Ascension: 40 days after Pascha (always a Thursday)
Pentecost: 50 days after Pascha (always a Sunday)
All Saints Sunday: The first Sunday after Pentecost
Apostles’ Fast begins: The Monday after All Saints Sunday

The Liturgical Year

September 1: The Church New Year (Indiction)

The liturgical year begins on September 1 (OS) / September 14 (NS). This date is called the Indiction (Indikt), after the Roman imperial tax cycle. The first fixed Great Feast of the year is the Nativity of the Theotokos (September 8/21), and the last is the Dormition of the Theotokos (August 15/28). Thus, the liturgical year is framed by feasts of the Mother of God.

September 1 is observed liturgically with a special service, but it is not a major feast. The hymns for the day speak of Christ’s reading from Isaiah in the synagogue at Nazareth (Luke 4:16-21): “The Spirit of the Lord is upon me…”

The Three Liturgical Cycles

The Church year is governed by three interlocking cycles:

1. The Fixed Cycle (Menaion)

The Menaion (Minea) is a set of twelve volumes (one per month) containing the hymns and readings for every fixed feast and saint’s day. Fixed feasts occur on the same calendar date every year (e.g., Nativity of Christ is always December 25 OS). The Menaion provides the troparia, kontakia, canons, stichera, and readings for each day.

2. The Weekly Cycle (Octoechos)

The Octoechos (“Book of Eight Tones”) provides a weekly cycle of hymns in the eight ecclesiastical tones (glas). Each week is assigned one tone, cycling through all eight in order:

Week	Tone
1st week after Pentecost (All Saints)	Tone 1
2nd week	Tone 2
…	…
8th week	Tone 8
9th week	Tone 1 (cycle repeats)

The tones provide musical and textual variety throughout the year. Each tone has a complete set of hymns for every day of the week. The system was traditionally attributed to St. John of Damascus (8th century), though it developed over several centuries (Schmemann, Introduction to Liturgical Theology, ch. 5).

Within each week, each day also has a thematic dedication:

Sunday: The Resurrection
Monday: The Bodiless Powers (Angels)
Tuesday: St. John the Baptist
Wednesday: The Cross and the Theotokos (a fast day, commemorating the betrayal)
Thursday: The Apostles and St. Nicholas
Friday: The Cross and the Theotokos (a fast day, commemorating the Crucifixion)
Saturday: All Saints and the Departed

3. The Paschal Cycle (Triodion and Pentecostarion)

The Triodion (Postnaya Triod’, “Lenten Triodion”) covers the period from the Sunday of the Publican and Pharisee (the beginning of the preparatory weeks before Great Lent) through Holy Saturday. The name comes from the fact that the canons at Matins during this period have only three odes (tri-odi) instead of the usual nine.

The Pentecostarion (Tsvetnaya Triod’, “Flowery Triodion”) covers the period from Pascha through the Sunday of All Saints (the first Sunday after Pentecost). It contains the joyful hymns of the Paschal season.

Together, the Triodion and Pentecostarion form a continuous cycle of approximately 18-19 weeks centered on Pascha.

Moveable vs. Fixed Feasts

Fixed feasts occur on the same calendar date each year: Nativity of Christ (Dec 25), Theophany (Jan 6), Annunciation (Mar 25), Transfiguration (Aug 6), etc.
Moveable feasts depend on the date of Pascha: Palm Sunday, Ascension, Pentecost, All Saints, etc.

The interaction between fixed and moveable feasts creates complex liturgical situations. For example, when the Annunciation (March 25 OS) falls during Holy Week or on Pascha itself – a rare occurrence called Kyriopascha – special rubrics govern how the services are combined. The Typikon provides detailed instructions (the so-called Markovye Glavy, “Markings Chapters,” attributed to the monk Mark) for handling these intersections.

Ranks of Feasts

The Typikon assigns feasts to a hierarchy of ranks, each with its own liturgical prescriptions:

Pascha – The Feast of Feasts, in a category by itself
Great Feasts (Dvenadesiaty Prazdniki, Twelve Great Feasts) – see Great Feasts
Middle Feasts – with Great Doxology at Matins (e.g., major saints’ days)
Lesser Feasts – with Polyeleos, or with Great Doxology, or with the singing of “God is the Lord” at Matins
Simple commemorations – ordinary weekday commemorations of saints

The Typikon uses special symbols (a cross in a circle, a cross in a half-circle, a red cross, etc.) to indicate the rank of each day.

References

Schmemann, Alexander. Introduction to Liturgical Theology. St. Vladimir’s Seminary Press, 1966.
Taft, Robert. The Byzantine Rite: A Short History. Liturgical Press, 1992.
Typikon (Ustav), chapters on the ordering of the Church year.
Bulgakov, Sergei V. Handbook for Church Servers (Nastolnaya Kniga). 2nd ed., 1900.
Kuzenkov, Pavel V. Khristianskie khronologicheskie sistemy: Istoriia letoschisleniia v sviatootecheskoi i vostochnokhristianskoi traditsii III-XV vekov [Christian Chronological Systems: The History of Time-Reckoning in the Patristic and Eastern Christian Tradition]. Moscow: Russkii izdatel’skii tsentr, 2014.
Skaballanovich, Mikhail. Tolkovyi Tipikon [The Explanatory Typikon]. 3 vols. Kiev, 1910-1915. (The standard Russian historical commentary on the Typikon.)
Patsavos, Lewis J. “Dating Pascha in the Orthodox Church.” Greek Orthodox Archdiocese of America (goarch.org).