But I point out in my Jewish Holy Days post that the Fall Feasts did have relevance to the First Advent. And there is no Biblical basis for God ever intending a return to Tishri-Tishri years, Ezekiel 45 clearly sees the future messianic era as Nisan-Nisan years.
Even when I did feel pretty strongly that the 70th week would be Tishri years I still considered that both the Rosh Hoshana view and Seventh Trumpet view of the Last Trump could both be correct. That the Seventh Trumpet isn't the exact half way point like the Abomination is, but perhaps the beginning of the 4th year, or the end of the 4th year. Now however I've decided the 7th Trumpet must be close to the Resurrection of The Witnesses and thus to the Abomination of Desolation.
I still think it could be Tishi-Tishri years, we'll know once the Temple is rebuilt, because I'm not currently negotiable on that the consecration of the rebuilt Temple is what officially begins the 70th week. Those who think The Temple will still be under construction during the first 3 and a half years are unwittingly setting the stage for The Beast to device people with a counterfeit 70th Week.
The main thing that had me firmly viewing them as Tishri-Tishri years was that Solomon's Temple was consecrated on Yom Kippur, and so I figured both the Third Temple and "Millennial Temple" (which I still assumed was Ezekiel's), will likewise be consecrated on Yom Kippur. But now I view Ezekiel 40-48 and certain other assumed OT Prophecies of the Millennium as actually being the new Heaven and New Earth, I have a thread on that.
The Second Temple had a history firmly linked to Nisan as studying the 70 Weeks shows, even the incorrect views on it, pretty much all the possible decrees were issued in Nisan. And for many reasons, the next Temple is more like the Second then the First. The 3rd of Adar was the day the second Temple was completed, just in time to begin a Biblical year.
One extra Biblical assumption about the Feast of Trumpets/Rosh Hoshanna/First of Tishri, that I can't find actual Biblical Support for is the commonly stated claim of it being a day affiliated with Coronations.
In fact Biblical clues seem to show Nisan as being the "New year for Kings". The following quote from The Jewish Voice further clarifies this view:
"How do we know that Passover is Rosh HaShanah for the Kings? It is in the Tanach [Old Testament], though somewhat hidden. How do we know that the Kings of Israel are crowned at Passover? In I Kings, it says this: ‘… in the fourth year of Solomon’s reign over Israel, in the month of Zif, which is the second month, that he began to build the House of Adonai.’ (I Kings 6:1) It is repeated in II Chronicles 3:2 as well. The second month of the reign of King Solomon – which means Solomon was crowned the month before! The month of Zif is now known as the month of Iyar, which comes after the month of Nisan, when Passover is. From this understanding, we can check it with the other kings of Israel as well. There was a debate between the House of Hillel and the House of Shamai, whether it was on the 15th or the 1st of the month, but the 15th is Passover night, and this became the common understanding."The notion of Coronations being affiliated with Passover should be very interesting to Christians. Because it was on the 14th of Nisan 30 AD that Jesus was Crowned with a Crown of Thorns, and given a Royal Robe and mocked for being a King. And on the Cross was officially proclaimed by Pilate Jesus of Nazareth, King of The Jews.
At the beginning of the 70th Week, The White Horsemen is given a Crown when the First Seal is opened. And at the end, when Jesus returns also riding a White Horse he will have many crowns upon his head.
What all this means is we may need to consider the Prophetic significance of the Fall Feasts as being in the Middle of the 70th Week, not it's end. Hence possibly in the fulfillment of the Mid-Trib/Seventh Trumpet view of The Rapture.
David had two Coronations, one in Hebron when he was 30, and one 7 years later in Jerusalem. Also Ish-Bosheth was crowned around the same time as David's first coronation. So the Eschatological Week having Coronations in Nisan at it's beginning and ending could be interesting. Ish-Bosheth could arguably be viewed as a type of the Antichrist.
Jesus also had a Coronation, with a Crown of Thrones, at the end of 69 Weeks. So perhaps His formal Millennial Coronation will be in Nisan when the Eschatological 7 years are over.
The Karaites also know that the year begins and ends with Nisan.