It seems I read somewhere that after the birth of Christ two months were added to the calender. July and August..???
Interesting that the our 9th month September (=7) is the 7th month of the Jewish calendar...October, our 10th month (=octagon=8) is the eighth month of the Jewish calendar...
I don't know about November but our 12th month, December, =Deci.=10...Our December is the 10th month of the Jewish calendar...