Fay posted a link to Stephanie Dawn's four part study of Pentecost on unsealed.org. Part 3 deals with the unknown date question.
Here is another study , going verse by verse , taking the same position that Pentecost is the only feast with an unknown date.
There are several interesting things pointing to May 30-31 , 2020.
1. It is 666 days from Obama's Birthday Aug. 4, 2018 to and including May 30, 2020.2. It is 1260 days after the beginning of the "Great Sign in the Heavens" of Rev. 12( Nov. 16, 2016) to May 30 , 2020. But Nov 16, 2016 was also Chesvan 17 , the Day Noah's flood began.3. It is Chesvan 27 on Nov 11, 2023 , the day Noah's flood ended if you go forward 1260 days. "As it was during the days of Noah" Mt 24:374. The Church came into being on Pentecost. Acts. Shall it end the same day ?5 Enoch , by tradition, was both born and "taken by God" on Pentecost. Enoch is a type of the church , his name meaning "dedicated or teaching", a church function.6. Daniel 12:9 says "Go thy way Daniel for the words are sealed until the time of the end"."Daniel" is Strongs word H1840. "Time" is H2165. The total is 4005 which is "Pentecost"7. David, by tradition was born and died on the same day , Pentecost. He was 70 years old at death. Israel signed its final peace treaty with Syria on July 20, 1949 and had conquered its final foe that day. Pentecost was June 2, 1949 so Israel's first Pentecost in peace was a year later in 1950 , now 70 years ago.8. The timeline of Daniel , chapters 9 and 12 fit..... 1260, 1290, and 1335 days.
Order to to restore Israel ; UN Resolution 181 Nov 29, 1947. Add 62 years is...
Oct 9, 2009 Obama receives the Nobel Peace Prize based on "what he is going to do"., a covenant with many....Now add 1260 days.
Obama stands in the Church of the Nativity, Bethlehem March 22, 2013. An abomination, standing in the holy place. Mt 24:15
Add 1290 days (Dan 12:11). is Oct 3, 2016 , the Feast of Trumpets, beginning the Jewish civil year. Obama is quoted today : "Republicans think I am the Antichrist" (Fox News). Obama is indirect. Like Christ, indirect, "Others say" Mt. 16:13. "But who do you say I am?"
Add 1335 additional days (Daniel 12:12) is May 28-30--- Pentecost