First off I agree that Rosh Hashanah, the first day of the new year. This is the day that Christ was born. Between the darkness of Elul 29 and Tishri 1, The new day, and new year.
Christ's birth fulfilling the fall Feast of Trumpets, His birth appointed on Tishri 1, 25bce or modern terms of September 12/13, 25 bce. This is his date of BIRTH.
Considering that Christ was born on this date, we can go farther with this date and SHOW that according to Daniel's visions, this date has been fulfilled and is over 2000+ years ago. This can be figured accurately by counting backwards from 70ad when the temple was destroyed in 70ad. Has nothing to do with other festivals, as for counting this date out we do not have to guess on any of the so called timelines.
Christ born in 25 bce to 70ad when the temple was destroyed is this is 95 years, although it must be broken down as Daniel's prophecy shows. 70ad minus the 3 years of The Great Tribulation is 3 years, that brings us to 67ad, When Phannias ben Samuel, 67-70 had been ELECTED as HIGH Priest which is not legal under the law, as God appointed High Priest they were not elected by the people as this one was. He was considered the false Prophet, or antichrist sitting where he should not be, as Christ is High Priest, this is the sign the people were to look for, as they knew the man had been elected and not appointed as under the law, violating the Commandments give to appoint High Priests. God fully warns us of this day, though many think this some sort of secret. So, 70 ad minus 3 years for Tribulation brings us to the 67ad point that Phannias ben Samuel, was appointed by the people. If you take a generation which is 40 years, according to the walkings in the wilderness for punishment and not allowed to go over the Jordan. This same 40 years was given to those in Israel in that last generation from 27ad to 66ad is 27 years but the temple was without High Priest for almost a year. So that brings us to 66ad instead of 67ad. Considering 66ad taking away the 40 years brings us to 26ad, the exact year Christ was crucified on, being April 19, 26, this is 40 years. This is not hard to compute it is confusing if one does not teak into account the Jewish ways. I have been studying this for over 40 years and am just now getting the full picture as before I could understand this God had to show me all the connections that I did not have when I began. Blessings........