The Orthodox Church eventually recognized the civil New Year from the old Roman calendar and both adapted and adopted this into the Church’s calendar making September 1 the “Church’s” New Year’s Day. Spiritually it seems strange, because I would say liturgically Pascha is the Church’s New Year for on that day we proclaim the beginning of our life in Christ and the beginning of the Church as is obvious in our Scripture readings from John 1 and Acts 1. In the Bible, the New Year also begins in the Spring right before Passover. God clearly commands Moses, Aaron and thus all of Israel: “This month shall be for you the beginning of months; it shall be the first month of the year for you” (Exodus 12:2). [Judaism though also has a “religious” New Year in the Spring as commanded in the Torah but also a civil New Year, Rosh Hashanah in the autumn].
It seems more that September 1 was simply the Church accepting the civil calendar from the Roman government under which it operated. We actually date things throughout the year liturgically as “after Pascha” and then “after Pentecost” (which is dependent on Pascha), not after September 1. The September 1 New Year Day has never seemed that important to me. Some today like to point out that the Birth of the Theotokos is the first Major Feast of the September 1 New Year calendar and August 15 is the Dormition of the Theotokos, so that her birth and death are the bookends of all Twelve Major Feasts. But I don’t know if that is an accidental coincidence or was intentionally designed that way, nor do I know when that idea that Feasts of the Theotokos begin and end the year was first mentioned in Orthodox literature, so I don’t even know if it is simply a modern observation or an older idea. Many pious explanations seem ancient but turn out to be more modern rationalizations for why things are the way they are.
Be that as it may, here is a quote for us to consider for the Church’s New Year. Genesis starts “In the beginning…” and it is frequently said that God started the first New Year’s Day by building Himself a temple.
“My thoughts turned to the book of Genesis. From the opening verses of Genesis through to the books of Psalms and the Prophets, the Old Testament envisions the whole of Creation, heaven and earth, as a vast temple in which the people gather in liturgy to give praise and honor to the Maker and thank him for the beauty and goodness of his Creation. God lays the foundations (Ps. 104:5), sets up the pillars (1 Sam. 2:8), stretches out the canopy (Isa. 40:22), and frames the windows (Mal. 3:10). He is enthroned within the temple, as heavenly and earthly choirs glorify his name.” (Vigen Guroian, The Melody of Faith: Theology in an Orthodox Key, Kindle Loc. 73-76)