India couple stands as they watch the last sunset of 2012 over the shores of the Arabian sea in Mumbai, India, Monday, Dec. 31, 2012.(AP Photo/Rafiq Maqbool)
Iraqi tourists pose for a photograph in front of a Christmas tree as they celebrate the New Year during a countdown event in downtown Beirut, Lebanon, Tuesday, Jan. 1, 2013. (AP Photo/Bilal Hussein)
Fireworks explode in the sky above Sydney Harbour during the pre New Years Eve celebrations in Sydney, Australia, Monday, Dec. 31, 2012.(AP Photo/Rob Griffith)
Fireworks explode in the sky over St. Basil Cathedral as Russians celebrate New Year on Red Square in Moscow, Russia, on Tuesday, Jan. 1, 2013. (AP Photo/Ivan Sekretarev)
The fireworks explode as the Waterford crystal ball is raised at the beginning of Times Square New Year's celebration, Monday, Dec. 31, 2012 in New York. (AP Photo/Mary Altaffer)
Here's something to ponder as you celebrate the New Year: Why does the old year end in December and the new one begin in January?
Technically, the new year could start in any month, after all.
Why not spring, for instance, when plants start coming back to life? Why not Dec. 21, which marks the winter solstice?
Or why not on Dec. 25, considering the years are numbered from the birth of Christ?
The answer, it turns out, traces back to the Romans, when Julius Caesar was putting together the Julian calendar in 46 B.C.
He picked the date for the Roman god Janus, the two-faced ruler of doors and gates. He thought January, named after Janus, was an appropriate way to mark the doorway between two years.
After Rome fell and Christianity spread, the Jan. 1 New Year's holiday -- which the Romans typically celebrated with drunken revelry -- turned somewhat chaotic.
The early Christians considered it a pagan holiday. So some Christian countries started marking the new year on March 25, the day Mary was
told that she was miraculously pregnant with Jesus. And others decided Christmas Day or Easter Sunday were more fitting.
By 1582, Pope Gregory XIII got sick of the chaos -- and the fact that the Roman calendar didn't quite nail the nuances of the 365-day year -- so he created a new calendar that included a leap day every four years. During the process of creating the modern Gregorian calendar, he also restored the New Years holiday to Jan. 1.
Even today, though, not every culture agrees that Jan. 1 is the best day to mark the new year.
Many other cultures use a variety of lunar or combined lunar-solar (lunisolar) calendars, and the way they mark a new year varies widely.
Chinese New Years occurs on the new moon of the first lunar month, which falls between Jan. 21 and Feb. 21 on the Gregorian calendar. The Chinese calendar doesn't generally include year numbers, but the Chinese year, depending on which scholar you talk to, is either 4710, 4709, or 4649 -- not 2012. The next Chinese New Year begins Sunday, Feb. 10, 2013.
The Tibetans like to ring in their New Year with a 15-day celebration called the Losar, which often occurs in February and is also based on a lunisolar calendar that's slightly different than the Chinese one. The next Losar begins on Monday, Feb. 11, 2013.
The Jewish New Year, Rosh Hashanah, starts on the first day of Tishrei, the first month of the lunisolar Jewish calendar. The day is believed to mark the anniversary of when Adam and Eve were created. The next Rosh Hashanah runs from sunset Wednesday, Sept. 4. to nightfall Friday, Sept. 6, 2013. and will mark the start of the year 5774.
Many Arabic countries celebrate the Hijri New Year. The Hijri is part of the Islamic calendar, also based on lunar cycles. The first year of the Islamic calendar marks when Muhammad emigrated from Mecca to Medina, in 610 A.D. The next Hijri New Year's day, which will mark the beginning of the year 1435, will fall from sunset on Nov. 4 to sunset on Nov. 5, 2013.