January 25th is the feast of the Conversion of St. Paul and the end of the Week of Prayer for Christian Unity.
What does one have to do with the other?
The Week of Prayer for Christian Unity consists of eight days beginning January 18th, the feast of the Chair of Peter, and ending on January 25th, the feast of the Conversion of St. Paul. The Franciscan Friars of the Atonement, founded in the early 20th century in Graymoor, New York, sought to promote unity among Anglicans and Roman Catholics. Paul James Wattson, a former Episcopalian priest, founded the community, which was formally accepted into the Catholic communion.
The idea for Christian unity soon began to catch on, and by the 1930s, more and more Christians welcomed such a focus. Suggestions for prayer and education are distributed each year, emphasizing a jointly chosen theme. The 1964 Vatican II document on ecumenism, Unitatis Redintegratio, gave a great boost to the octave, so that today many Christians worldwide promote and participate in the octave time of prayer.
The emphasis on both Peter and Paul aptly fits into the rationale of the octave. Peter is seen as the source of unity within the Christian tradition. Paul is highlighted due to his vision of bringing all to Christ. The Week of Prayer for Christian Unity is an ideal opportunity to pray for and promote respect, understanding, and, hopefully, eventual unity among Christians.