What is the origin of New Years Day?
New Year’s Day was established on January 1st in 153 BC in the Late Roman Republic by the Roman senate. Prior to this, New Year’s was always celebrated in spring since the time coincided with the the rebirth of crops and blossoming. The January 1st date was more formally adopted when the Julian calendar was established by Julius Caesar.
Because the early Catholic Church condemned New Year’s celebrations as paganism, it was only gradually adopted by Christianity. The Western world has only been celebrating New Year’s for the past 400 years or so.
Info from: http://www.wilstar.com/holidays/newyear.htm