Rooted in the Roman and Gregorian calenders, the designation of January 1 as New Year's Day is a product of political and religious rangling over the years. More in tune with the forces of nature, the ancient Greeks accepted the winter solstice as the beginning of their new year.
Afterall, life on earth is dependent upon light and heat from the sun and the solstice is a rebirth of the solar cycle. Of course, for those in the southern Hemisphere, this event occurs at the time of our summer solstice (on or about June 21). So, while this is the first day of the human year, it is day eleven (or so) in the natural cycle of our Hemisphere.