What is the Mormon take on the Day of Pentecost?

Answer 1

As for the Mormon Day of Pentecost ("Birthday of the Church"):

At the meeting were four other men, in addition to Joseph and Oliver, who had been selected to become incorporators of the Church, "agreeable to the laws of our country." (D&C 20:1.) They are listed in the History of the Church as Hyrum and Samuel H. Smith, brothers of Joseph, and David and Peter Whitmer, Jr., sons of the man who had opened his home for the organization meeting. All had previously been baptized.

In addition, there were a "few" friends who had been invited to attend, perhaps not more than thirty altogether. Among these were the Prophet's father, Joseph Smith, Sr., and his beloved mother, Lucy Mack Smith. Both had believed his story and had encouraged him in the work from the beginning.

No original minutes are available of the proceedings of the day, and there is perhaps a question about the exact order in which some of the events occurred, but there is agreement on what transpired.

While Mormons make note of the birthday of the Mormon church, it is not celebrated with any feasts.

Mormons do believe The Bible and Acts 2 which talks about Pentecost which is celebrated by many churches and countries, but Mormons do not hold Pentecostal feasts or celebrations in the United States but may vary according to cultural norms in the country they are in.

Since the Mormons believe the Bible, they also believe in Moses delivering the Ten Commandments to the people which is recognized as the Jewish Day of Pentecost, but again do not hold any special feasts or celebrations.