The Julian calendar takes effect as the civil calendar of the Roman Republic, establishing January 1 as the new date of the new year.

The Julian calendar is a solar calendar of 365 days in every year with an additional leap day every fourth year. The Julian calendar is still used as a religious calendar in parts of the Eastern Orthodox Church and in parts of Oriental Orthodoxy as well as by the Amazigh people. For a quick calculation, between 1901 and 2099 the much more common Gregorian date equals the Julian date plus 13 days.

January 1 is the first day of the calendar year in the Gregorian Calendar; 364 days remain until the end of the year. This day is also known as New Year's Day since the day marks the beginning of the year.