As was mentioned, according to Holy Tradition, Christ entered the synagogue on September 1 to announce His mission to mankind (Luke 4:16-22). After reading this passage, Jesus announced to the assembly that this prophecy had been fulfilled in Him that day, right before their eyes, confirming His Messianic role. Although we cannot forensically confirm that date, it is spiritually significant that the Church has joined the first day of Jesus’ public ministry with the first day of the New Year in her rhythm of worship.
Tradition also says that the Hebrews entered the Promised Land in September. Fascinating right? The Orthodox Church in many respects keeps the calendar of the Byzantine Empire. Under a system instigated by the Emperor St. Constantine the Great in the 4th century, the Indiction was a 15-year taxation cycle that began on September 1. Over time, this date came to be popularly observed throughout the Empire as the start of the New Year because it meant the beginning of a new period of taxation. The Church adopted this observance as well.