New Year's Day, at least in the Gregorian calendar, is something of an oddity among holidays.
You see, when you break it down, any other recurring holiday falls into one of three categories: celebrating a historical anniversary, celebrating a particular group of people or things, or celebrating a seasonal event. The first category covers the majority of holidays, including events political (Independence Day, Guy Fawkes Day), religious (Christmas, Easter), or personal (anyone's birthday). The second category covers most of the rest, including holidays celebrating a particular nationality or culture (Saint Patrick's Day, Kwanzaa) or a particular occupation or role (Valentine's Day, Veterans' Day), as well as particular non-human things (Arbor Day, Earth Day). The third category, which includes all the equinoxes and solstices, is rarely observed in the Western world today, although some lesser holidays like May Day (the arrival of spring) or Oktoberfest (the arrival of the fall harvest) preserve it.
Some holidays straddle two categories, or have evolved from one to the other. Valentine's Day was once Saint Valentine's Day, but has become a day to celebrate the beloved people in our lives instead of St. Valentine himself. But New Year's Eve/Day falls into a fourth category: it is the only major mathematical holiday, which observes nothing more than the changing of all the numbers on our clocks and calendars at once. (There's also Pi Day, which celebrates a similar numerical coincidence, but that holiday has yet to make it onto the common calendar.) The new year coincides with no major seasonal event*, no historical event, and is equally observable by all peoples who recognize January 1. It is a celebration of the once-a-year event when the slowest-moving number on our clock ticks forward another notch. And that's all.
It is, in my opinion, either a symbol of civilization's greatest scientific accomplishment--the invention of abstract numbers with which to measure the universe--or a demonstration of its greatest absurdity, the celebration of nothing at all. Quite likely it is both.
Happy New Year to all, then, and may our clocks continue to tick forward with the same reliable synchronicity in the coming planetary cycle.
* After composing this writeup, I noticed that January 1, 2005 is the exact date of Earth's perihelion, its closest approach to the sun, and that this event occurs on or near January 1 every year. As far as I can find out, though, this is a lucky coincidence. The Gregorian calendar was scheduled primarily so that the drifting Easter holiday would always occur near the vernal equinox.