Julius Caesar introduced the Julian Calendar in 45BC and fixed January 1 as the first day of the year. It is now marked with celebrations in many cultures. It marks the new calendar year and the calendar’s year count is increased by one. Roman dictator, Julius Caesar changed the traditional Roman calendar because he felt it was in dire need of reform. The previous calendar, the Roman calendar, attempted to follow the lunar cycle but frequently fell out of phase with the seasons and had to be corrected often.
He year was calculated to be 365 and 1/4 days, and Caesar added 67 days to 45 B.C., making 46 B.C. begin on January 1, rather than in March. He also decreed that every four years a day be added to February, thus theoretically keeping his calendar from falling out of step. Shortly before his assassination in 44 B.C., he changed the name of the month Quintilis to Julius (July) after himself. Later, the month of Sextilis was renamed Augustus (August) after his successor. – History