From Peter the Great: His Life and World, about which I will write more later, …
Since the earliest times, Russians had calculated the year not from the birth of Christ but from the moment when they believed the world had been created. Accordingly, by their reckoning, Peter returned from the West not in the year 1698 but in the year 7206. Similarly, Russians began the New Year not on January 1, but on September 1. This stemmed from their belief that the world was created in autumn when the grain and other fruits of the earth had ripened to perfection and were ready to pluck, rather than in the middle of winter when the earth was covered with snow. Traditionally, New Year’s Day, September 1, was celebrated with great ceremony, with the tsar and the patriarch seated on two thrones in a courtyard of the Kremlin surrounded by crowds of boyars and people. Peter had suspended these rites as obsolete, but September 1 still remained the beginning of the New Year.
But to blunt the argument of those who said that God could not have made the earth in the depth of winter, Peter invited them “to view the map of the globe, and, in a pleasant temper, gave them to understand that Russia was not all the world and that what was winter with them was, at the same time, always summer in those places beyond the equator.” To celebrate the change and impress the new day on the Muscovites, Peter ordered special New Year’s services held in all the churches on January 1. Further, he instructed that festive evergreen branches be used to decorate the doorposts in interiors of houses, and he commanded that all citizens of Moscow should “display their happiness by loudly congratulating” one another on the New Year. All houses were to be illuminated and open for feasting for seven days.
To be honest, I think the old Russian New Year reasoning made sense, although Peter was correct about the seasons.
That was the Byzantine calendar. Based on Anno Mundi, just like the Hebrew calendar.