How is the date of Great Lent determined every year?
By CopticBot.ai (Coptic Space Inc.) · Last reviewed 2026-10-10
In the Coptic Orthodox Church, the calculation of the dates for Great Lent and the Feast of the Resurrection is governed by a precise mathematical and astronomical system known as the Epact.
This system was finalized by the 12th Pope of Alexandria, St. Demetrius the Vinedresser, who was inspired by the Holy Spirit to establish a unified date for Easter so that all Christians might celebrate at the same time. This calculation was later adopted by the Ecumenical Council of Nicea (AD 325) and remains the standard for the Orthodox world.
The date of Great Lent is determined by counting backward from the date of the Resurrection, which is calculated based on three primary factors:
1. The Vernal Equinox
The Feast of the Resurrection must occur after the Vernal Equinox (March 21 in the Julian calendar, which corresponds to the Coptic month of Paremhotep). This ensures that the feast is celebrated in the spring, symbolizing new life.
2. The Jewish Passover
According to the Decree of the Council of Nicea, the Christian Passover (Easter) must strictly occur after the Jewish Passover (14th of Nisan). Since Christ is the True Lamb of God who fulfilled the Law, it is chronologically and theologically necessary that the reality (the Resurrection) follow the symbol (the Old Testament Passover). This is why the Orthodox date often differs from the Western (Catholic/Protestant) date, as the Western calculation sometimes allows Easter to fall on or before the Jewish Passover—a practice we reject as historically and theologically incorrect.
3. The Full Moon
The Resurrection is celebrated on the first Sunday following the first full moon that occurs after the Vernal Equinox. This maintains the biblical connection to the lunar calendar used in the time of our Lord's Passion.
Calculating the Start of Great Lent
Once the date of the Resurrection is determined, the Church counts backward to set the start of Great Lent:
- The 55 Days: Great Lent in the Coptic Church consists of 55 days in total.
- The Pre-Lenten Week (The Preparation Week): 7 days used to prepare the soul for the journey.
- The Forty Days (The Holy Quadragesima): 40 days in imitation of our Lord’s fast on the mountain (Matthew 4:2).
- Holy Passion Week: 8 days (from Lazarus Saturday to the Eve of the Resurrection).
- Counting Back:
- From the Sunday of the Resurrection, you count back 7 weeks (49 days) to reach the Monday that begins the First Week of Lent.
- Then, you count back an additional week to determine the date of Jonah’s Fast, which always begins exactly two weeks before the start of Great Lent.
The Role of the Pope of Alexandria
Historically, the Church of Alexandria was known as the "Teacher of the World" in matters of science and astronomy. Following the Council of Nicea, it became the responsibility of the Coptic Pope to calculate the date of the Resurrection each year and send "Festal Letters" to all other Sees (Rome, Antioch, Jerusalem, and Constantinople) to inform them of the correct date, ensuring the unity of the Church.
By following this Epact calculation, the Coptic Church ensures that our fast and our feast are rooted in the harmony of creation (the sun and moon), the fulfillment of Scripture (the Passover), and the tradition of the Holy Fathers.