The traditional period in the northern hemisphere for the Week of Prayer for Christian Unity is 18-25 January. Those dates were proposed in 1908 by Paul Wattson to cover the days between the feasts of St Peter and St Paul, and therefore have a symbolic significance. In the southern hemisphere where January is a vacation time churches often find other days to celebrate the week of prayer, for example around Pentecost (suggested by the Faith and Order movement in 1926), which is also a symbolic date for the unity of the church.
Mindful of the need for flexibility, the Pontifical Council for Promoting Christian Unity invites you to use this material throughout the whole year to express the degree of communion which the churches have already reached, and to pray together for that full unity which is Christ’s will.