The Outpouring of the Holy Spirit (Pentecost; May 25th, A.D. 33 ):
The Jewish festival of Pentecost (Shavuot or the Festival of Weeks) was one of the 3 mandatory Festivals of Pilgrimage for Jews, which required all the outlying Jews to travel to the temple in Jerusalem to observe it. Shavuot has a double significance for Jews. It marks the all-important wheat harvest in the Land of Israel (Exodus 34:22); and it commemorates the anniversary of the day God gave the Torah (i.e., the Law, the stone tablets of the Ten Commandments) to the nation of Israel who were assembled at Mount Sinai. It occurs 50 days after the Festival of the Passover.
On May the 15th in A.D. 33 the Ascension had occurred 40 days after the Resurrection of Christ, i.e. Ascension Thursday is 10 days prior to Pentecost (counting inclusively). On Pentecost in A.D. 33, God’s Holy Spirit descended on the Apostles and other followers of Jesus Christ (see Luke 22:12–13 & the Acts of the Apostles 2:1–31 ). It is not a coincidence that the day the Jews set aside to remember God giving them the Law became the day that Christians remember God giving us the Grace of the Holy Spirit !!