If Christians in East and West are united in their belief in the Resurrection, why then do they celebrate Easter on different dates? The reason is that two different calendars are used to calculate the date of Easter. One is the 16th-century Gregorian calendar, used mainly by Western churches. The other is the much older Julian calendar, used by most Orthodox churches. At present the Julian calendar differs from the Gregorian by 13 days; in the year 2100 it will be 14 days.

Especially in regions where Christians of the Western and Eastern traditions live closely together and may even constitute a minority, as for example in the Middle East, this situation is extremely painful.

One milestone in the efforts to establish a common date for Easter was the consultation held in Aleppo, Syria, in March 1997, jointly sponsored by the WCC and the Middle East Council of Churches. Of great importance was the recognition that differences in calculating the date of Easter do not depend on basic theological disagreements.

The consultation recommended that the principle of calculation recognized by both Eastern and Western churches and established by the Council of Nicea in the year 325 should be retained. According to this principle, Easter falls on the Sunday which follows the first full moon of spring. The Aleppo participants also recommended that the spring equinox be calculated "by the most accurate possible scientific means". Moreover, the basis for reckoning should be "the meridian of Jerusalem, the place of Christ's death and resurrection". This means a change for both East and West, as both calendars are astronomically inaccurate. For the churches using the Gregorian calendar a discrepancy would first occur in the year 2019: calculated by scientific methods, Easter in that year will fall on 24 March, but the Gregorian calendar will place it on 21 April, and the Julian on 28 April.

The Aleppo consultation saw the fact that the two dates for Easter would coincide at the start of the new millennium as an opportunity to continue and intensify efforts to establish a common date. "The celebration of Easter/Pascha on the same date should not be the exception but the rule". Hence the idea of reviewing the response to the Aleppo proposal in the year 2001.

How far have the churches gone in following the Aleppo proposals? The WCC Public Information Team has asked knowledgeable representatives of the Orthodox, Roman Catholic and Protestant traditions to give a brief outline of their thinking on a common date for Easter.

The series begins with an article by the Rev. Dagmar Heller, Executive Secretary for Mission and Ecumenical Relations in North Baden, Evangelical Church in Baden, Germany. Until recently a WCC staff member with the "Faith and Order" team, she has been involved in organizing and accompanying the discussion process on a common date for Easter. His Eminence Metropolitan Bishoy of Damiette of the Coptic Orthodox Church, Egypt, contributes from the viewpoint of the Oriental Orthodox tradition. Monsignor John A. Radano of the Pontifical Council for Promoting Christian Unity writes about "Catholic hopes of a common date for Easter". His Eminence Metropolitan Ambrosius of Oulu tells of the experiences of an Orthodox minority church in a Protestant country; in Finland "Orthodox and Lutherans have been experiencing the power of the Resurrection at the common date of Easter ever since the early 1920s".

• Celebrating Easter together by Rev. Dr Dagmar Heller

• Praying and working toward the common date of Easter: bringing us closer to the imperative of Christian unity by Metropolitan Bishoy of Damiette

• Celebrating together Redemption in Christ: Catholic hopes for a common date of Easter by Monsignor John A. Radano

• The gift of a common calendar - vital to mission and witness in secular society by Metropolitan Ambrosius of Oulu