"Out with the old and in with the new!"
It is said that New Year's is the oldest holiday that we still celebrate today, and just about every country, religion, and people celebrate it in some form.  The New Year was first recognized by paying attention to the cycles of the sun and moon and the changing of the seasons.  The Romans first declared January 1 to be the New Year.  Even in ancient times, resolutions and toasts were made at the beginning of the year.
Two fascinating websites with everything you should know about New Year's:
New Year's Day -- History, Traditions, and Customs

New Year's Day - Around the World