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
Adoption of the Gregorian calendar Austerlitz was the confusion between the Russians, who were using the Julian calendar, and the Austrians, who were using the Gregorian calendar, over the date that their forces should combine. However, this tale is not supported in a contemporary account from a major-general of the Austrian Imperial and Royal Army, who tells of a joint advance of the Russian and Austrian forces (in which he himself took part) five days before the battle, and it is explicitly rejected in Goetz's 2005 book-length study of the battle. The date when each country adopted the Gregorian calendar, or an equivalent, is marked