Pope Francis expressed his desire for all Christians to collectively celebrate Easter starting in 2025 when the date coincides for all Christian denominations. The Pontiff made this announcement during a meeting with representatives of the International Theological Commission of the Vatican, as reported by the Holy See press service.

Pope Francis considers it providential that the joint celebration of the Resurrection of Christ in 2025 aligns with the 1700th anniversary of the First Ecumenical Council held in Nicaea in 325 AD. "How can we not recall the exceptional significance of this jubilee on the path to the full unity of Christians?" remarked the Pontiff. "Not only does the Nicene Creed essentially unite the disciples of Jesus, but in 2025, the providential date of Easter celebration will coincide for all Christian denominations. How wonderful it would be if this became the concrete beginning of a perennial shared celebration of Easter!"

Addressing the representatives of the theological commission, Pope Francis called for a "rediscovery of the Nicene Council." This council established that Christians should celebrate Easter on the first Sunday after the first full moon following the vernal equinox. Different Churches calculate the date of the equinox differently. Currently, there are three calendar systems among Christian churches: the Julian, Gregorian, and New Julian calendars.

The Julian calendar, developed by Alexandrian astronomers and introduced by Julius Caesar on January 1, 45 BC, is used by some Orthodox Churches—Russian, Georgian, Serbian, Polish, Jerusalem, as well as Eastern Churches, including the Coptic and Ethiopian.

The Gregorian calendar, used by the Catholic and Protestant Churches, was approved by Pope Gregory III in 1582. Its introduction aimed to bring the date of the vernal equinox back to the March 21 date specified during the time of the First Ecumenical Council.

Due to the Earth's orbit around the Sun taking slightly more than 365 days, astronomical events can shift. The date of the vernal equinox, the day when the Earth's axis is strictly perpendicular to the Sun, also shifted. Pope Gregory's reform aimed to correct these discrepancies and restore astronomical events "to their original positions."

The difference in dates between the Gregorian and Julian calendars gradually increased, leading to the convening of the Fourth Ecumenical Council in 1923 by Patriarch Meletius IV of Constantinople. During this council, the New Julian calendar was introduced. The New Julian calendar will align completely with the Gregorian calendar for the next 800 years (until 2800). Orthodox Churches that adopted the New Julian calendar celebrate fixed holidays on Gregorian dates but calculate the date of Easter based on the Alexandrian paschal system, rooted in the Julian calendar.

The New Julian calendar is used by the Orthodox Churches of Constantinople, Cyprus, Greece, Poland, Romania, Alexandria, Antioch, Albania, and Bulgaria.