Happy Birthday to the Church of Jesus!
When the Day of Pentecost had fully come, they were all with one accord in one place. And suddenly there came a sound from heaven, as of a rushing mighty wind, and it filled the whole house where they were sitting. Then there appeared to them divided tongues, as of fire, and one sat upon each of them. And they were all filled with the Holy Spirit and began to speak with other tongues, as the Spirit gave them utterance. Acts 2:1-4
Although there is some dispute on when Pentecost occurs this year, the Hebrew calendar marks it down as May 29th and 30th, the Gregorian calendar as May 31st, and other calendars based on the stars as June 6-7.
Pentecost was not only the birth of the Church, but also the timing when God gave Moses the 10 commandments and confirmed a marriage covenant with Israel. I have written a few posts on Pentecost in the past and it's connection to a possible rapture
Also, this post from UNSEALED is very informative on Pentecost and what it means, past, present and future. I encourage you to study this wonderful holiday!