There is a link to a very good video at the bottom of this post.
I am thinking that though the Spirit came upon folks in Acts 2, that God, through the empowerment of the 120 followers of Jesus, was giving the nation of Israel/Judah a second chance to accept the earthbased kingdom centered on the Lord Jesus Christ. That Acts 2 was not initially the beginning of what we call the church age. When Peter quoted from Joel, the context of Joel that says, in 2:28, "It will come about after this . . ." is the earthly kingdom of Jesus that will be established after Israel/Judah returns to God after a time of refinement (see Joel 2 starting at verse 1, noting verse 17 in particular).
At the stoning of Stephen, I believe that was a mark in time of Judah rejecting the kingdom again, and is why the account of Saul/Paul starts at that time in Acts. In a way, that moment of Paul's conversion and the healing of his blindness by the one whose name means "grace", and this being done outside of the land of Israel/Judah, that that moment was, in a sense, when the church age started in an embryonic form. But at that moment of Paul's conversion, scattered Israel had not had the kingdom offered to them. That was in part what Paul going to accomplish through his travels. In other words, though the church age had "begun", it was not fully in place yet.
In total, there was to be a 40 year transitional time period.
The whole book of Acts is a laying out of that transition. It wasn't until the very last chapter of Acts, after Paul had gone all over the place proclaiming the kingdom centered on Jesus, both to Jews outside the land, as well as to Gentiles, that Paul proclaimed in that last chapter, that the focus would, from then on, be on the Gentiles. See Acts 28:24-28.
So when did that transitional period/season as detailed in the book of Acts officially end? Or, to put the question another way, when did the time of the church age fully get locked into place?
At the 9/10/11th of Av, when the temple was destroyed in 70 ad. I believe the church age was fully in place at that time. God made it very clear. There was no doubt.
I am thinking the true timing of the Feast of Pentecost is a Moed-themed timing of God having fully implemented a need for "new wine skins".
I am thinking that the confusion of languages at Babel was at the same time of year as Pentecost and is why in Acts 2, chosen ones within Israel/Judah were empowered to bridge that language barrier dating back to Babel. God was letting the world know that the nations who did not submit to God at Babel would only then be able to come to God through His chosen remnant within Israel/Judah.
I am thinking Pentecost is on/about the 1st day of the 5th month, being a counting of 7 sabbaths with an additional 50 days added on. Barry, in the video linked below, presents that it happens on the 9/10 of the 5th month. There is about a 10 day difference between us. I am not sure which understanding of Pentecost timing is most accurate. Even if it is about the 1st of the 5th like I am thinking, I also wonder if there will be a 10 day wait as I see hinted at in Genesis 24:55, Daniel 1:12-14, Revelation 2:8-11. I also wonder if in some way that because 10 days were removed in the changing of the calendars from Julian to Gregorian, that a particular count of days before God will need those 10 days "shoved back into" a timeline.
This year, the 9/10/11th of Av is mid August per the Jewish Hebcal. It is mid July per a calendar that has the Feast of Firstfruits on March 31st. It is also about June 19/20th on the constellation calendar that begun when the sun initially entered the 30 degree constellation night sky wedge of Aquarius. For this latter calendar, which I think applies specifically to the body of Christ, note what Paul says in II Timothy 4:6-8. His focus is about being done with his faith based walk on earth, about Jesus' coming, and about the longing of those who love Him. Within II Timothy 4:6-8 are clues that point to the names of stars in the constellation Aquarius and two of its related constellations of what is called today as Cygnus and Pegases. To discern this, read E W Bullingers book The Witness of the Stars. Note the names, and their meanings, of a number of stars in the constellations of Aquarius, Cygnus and Pegases and then compare those with the wording Paul uses in II Timothy 4:6-8. To me, Paul is hinting that we are to reference Aquarius for our calendar, which makes sense, since we are waiting to be completely filled and consumned by the indwelling Holy Spirit, so much so that our mortal bodies get transformed into immortal bodies by the indwelling I AM. It also makes sense to me that as new creations in Christ Jesus, which points to the time of the Father making a new creation Heaven and Earth after Jesus 1000 year reign, that at that time in the future (about the year 3030-ish), that the equinox will be in Aquarius, and is also why the four faces of the cheribim correspond to the equinox/soltice points of a constellation year that begins with Aquarius.
To me, the above, along with what Barry presents, points to a cool understanding of the timing and deeper meaning of the verses, "do not be drunk with wine . . but be filled with the Spirit."
God bless you.
https://youtu.be/pFbi8bNHSyU?si=kFKDPLgK8cfAkV_v