Tradition: Christianity-Orthodox
Link: http://www2.hds.harvard.edu/spiritual/multifaith_about.html
The commemoration of the coming of the Holy Spirit upon the disciples of Jesus following his ascension, Pentecost is considered the “birthday” of the Christian church (Acts 2:1–11). It comes 50 days after Easter (Pascha, Orthodox Easter). Roman Catholic and Protestant Christians observe Pentecost on a different date from Orthodox Christians.