The first instance of January 1 being celebrated as the first day of a new year goes back to the time of Julius Caesar, in 45 BC. Prior to that time, the Romans had used a lunar calendar. The first day of the year was usually in March, to coincide with the first day of Spring. Many cultures still have their new year start in the March timeframe but Caesar created January 1.
from Breaking Muscle http://ift.tt/2DL0l1F