Not quite 2000 years. Part of the Gregorian reform of 1582 was to move the beginning of the new year from March 25 (the Feast of the Annunciation) to January 1. In the Julian calendar September was indeed the seventh month after the beginning of the New Year, and so forth. March was the first (and last) month; April the second, and so on.
The Julian system was premised on the belief that the world was created on the same day that Jesus was conceived and the same day on which He was later Crucified.
Thanks for the update.
I feel lots smarter, now. ;)