When did people start celebrating new year's on the first of january?

•in 45 B.C., New Year’s Day is celebrated on January 1 for the first time in history
->as the Julian calendar takes effect

•in 1582, the Gregorian calendar was implemented,
->omitting 10 days for that year + establishing the new rule that only one of/ 4 (hundredth anniversary) years should be a leap year

•since then, people around the world have gathered en masse on January 1
->celebrate the precise arrival of the New Year