Week of Prayer for Christian Unity
At least once a year, many Christians become aware of the great diversity of ways of adoring God. Hearts are touched, and people realize that their neighbours' ways are not so strange.
The event that touches off this special experience is something called the Week of Prayer for Christian Unity. Traditionally celebrated between 18-25 January (in the northern hemisphere) or at Pentecost (in the southern hemisphere), the Week of Prayer enters into congregations and parishes all over the world. Pulpits are exchanged, and special ecumenical celebrations and prayer services are arranged.
For more information, check out this link.