The earliest recorded New Year's celebration is thought to be in Mespotania around 2000 BC with an 11 day festival.
The ancient Roman calendar used to follow the Lunar cycle and had the New Year beginning in March. Sosigenes, an astronomer, convinced Julius Caesar to follow the solar year. From 46 BC, on, the new year began in January.
Starting the New Year in January was partially done to honor the god Janus, for whom the month was named. Since Janus had two faces, he was able to look back into the past and forward into the future simultaneously.