Pentecost - Trinity Sunday in Russia (the 50th day after Easter)
This is a feast commemorating the descent of the Holy Spirit upon the Apostles and other followers of Jesus Christ as described in the Acts of the Apostles 2:1–31. For this reason, Pentecost is sometimes described by some Christians today as the "Birthday of the Church."
In Russian churches on this day you can see special descriptions - twigs of trees or small trees, flowers. The priests' clothing is green as well. It symbolizes the Vivifying Holy Spirit, alive church. Some people bring twigs or flowers with themselves and during the feast service everything is green and full of energy.