The earliest known calendars there, established by the first king, Romulus ... and the civil year in Rome now officially began on January 1. The Julian calendar also introduced an extra day ...

and when he created the Julian calendar, he made January 1 the first day of the year (this also put the calendar year in line with the consular year, as new consuls also took office that day).

Caesar’s calendar length was a little off ... Starting the new year on the first of January feels counterintuitive. We mark a fresh beginning in the dead of winter, when the days are shorter ...