when did the calendar change from 10 to 12 months
Roman calendar
24 a.d. IX Kal . The 9th Day before the Kalends ante diem nonum Kalendas a.d. VIII Kal . a.d. VII Kal . a.d. VI Kal . Mart .
24 a.d. IX Kal . The 9th Day before the Kalends ante diem nonum Kalendas a.d. VIII Kal . a.d. VII Kal . a.d. VI Kal . Mart .