January 1 was marked as the first day of the year in Ancient Rome; since the year 45 BC, with the Julian calendar.
In mediaeval times New Year's day was abolished because as it was considered to be a pagan celebration and moved to March 1.
January 1 became the first day of the year again in the Gregorian calendar in 1582.
Today many countries celebrate New Year's Day on different days of the calendar.