Gregorian calendar Gregorian equivalent of 29 February (Julian), to remember that 29 February is discounted. Thus if the calculated value is −4 the Gregorian equivalent of this date is 24 February. The year used in dates during the Roman Republic and the Roman Empire was the consular year, which began on the day when consuls first entered office—probably 1 May before 222 BC, 15 March from 222 BC and 1 January from 153 BC. The Julian calendar, which began in 45 BC, continued to use 1 January as the first day of the new year. Even though the year used for dates
December (Roman month) December (Roman month) December (from Latin "decem", "ten") or mensis December was originally the tenth month of the Roman calendar, following November ("novem", "nine") and preceding Ianuarius. It had 29 days. When the calendar was reformed to create a 12-month year starting in Ianuarius, December became the twelfth month, but retained its name, as did the other numbered months from Quintilis (July) through December. Its length was increased to 31 days under the Julian calendar reform. The Romans did not number days of a month sequentially from the first day through the last. Instead, they counted back from the three