New Year's Day is observed on January 1, the first day of the year on the modern Gregorian calendar as well as the Julian calendar.
Mesopotamia (Iraq) instituted the concept of celebrating the new year 2000 BC. The Romans dedicated New Year's Day to Janus, the pagan god of gates, doors, and beginnings, for whom the first month of the year, January, is also named. The pagan deity Janus was depicted as having two faces: one looking forward and the other backward, suggesting that celebrations of the new year are pagan traditions. Some suggested this occurred in 153 BC, when it was stipulated that the two annual consuls, after whose names the Romans identified the years, acceded to office on that day, though there is no consensus on the question. After Julius Caesar reformed the calendar in 46 BC as the Julian Calendar and was subsequently murdered, the Roman Senate voted to deify him on 1 January 42 BC, in honor of his life and his institution of the new rationalized calendar.
Most nations of Western Europe officially adopted 1 January as New Year's Day somewhat before they adopted the Gregorian Calendar. In England, until the adoption of the Gregorian Calendar in 1752, the first day of the new year was the Catholic Feast of the Annunciation, on 25 March, also called "Lady Day". Dates predicated on the year beginning on 25 March became known as Annunciation Style dates, while dates of the Gregorian Calendar commencing on 1 January were distinguished as Circumcision Style dates, because this was the date of the Feast of the Circumcision, the observed memorial of the eighth day of Jesus Christ's life after his birth, counted from the latter's observation on Christmas, 25 December. Pope Gregory christened 1 January as the beginning of the new year according to his reform of the Catholic Liturgical Calendar.
The celebrations held world-wide on January 1 as part of New Year's Day commonly include the following:
American football: In the United States, January 1 is the traditional date for many post-season college football games, which are usually accompanied by parades and other activities to celebrate the events
Football: In Europe is usually played throughout the Premier League and the rest of the League/Non League system in England
Ice hockey, most famously the Winter Classic in North America, a National Hockey League game that is played outdoors
Entertainment, usually enjoyed from the comfort of home
An annual dip in ice-cold water by hearty individuals, most famously by members of the Polar Bear Club