The Mayans seem to be taking most of the brunt of this frenzy, with many people pointing to them as prophesying the end of the world in 2012. However, what is this based on? Apparently it's a bunch of half-truths and poor understandings that are rooted in (what appears to me) a rock-hard belief in the power of numbers and that great social construction (originally meant to predict celestial events): the calendar.
So what, then, should we know about the Mayan long count calendar that makes 2012 so worrisome (or not so worrisome)? Well, (if we can trust Wikipedia as a source on the facts about what the calendar is):
The Mesoamerican Long Count calendar is a non-repeating, vigesimal (base-20) and base-18 calendar used by several Pre-Columbian Mesoamerican cultures, most notably the Maya. For this reason, it is sometimes known as the Maya (or Mayan) Long Count calendar. Using a modified vigesimal tally, the Long Count calendar identifies a day by counting the number of days passed since a mythical creation date that corresponds to August 11, 3114 BCE in the Gregorian calendar.[n 1] The Long Count calendar was widely used on monuments.Okay, so what, though? Well, a b'ak'tun is equivalent to 144,000 days, roughly 394.3 solar years, and (according to the Mayans) it took 13 b'ak'tuns to create the world (way back on August 11, 3114 BCE), and thus started the beginning of the current human period. December 20, 2012 is the completion of 13 b'ak'tuns since the beginning of the current period, which means...
The Long Count calendar identifies a date by counting the number of days from a starting date that is generally calculated to be August 11, 3114 BCE in the proleptic Gregorian calendar or September 6 in the Julian calendar (or −3113 in astronomical year numbering). There has been much debate over the precise correlation between the Western calendars and the Long Count calendars. The August 11 date is based on the GMT correlation (see Correlations between Western calendars and the Long Count calendar section elsewhere in this article for details on correlations).
The completion of 13 b'ak'tuns (August 11, 3114 BCE) marks the Creation of the world of human beings according to the Maya. On this day, Raised-up-Sky-Lord caused three stones to be set by associated gods at Lying-Down-Sky, First-Three-Stone-Place. Because the sky still lay on the primordial sea, it was black. The setting of the three stones centered the cosmos which allowed the sky to be raised, revealing the sun.
Rather than using a base-10 scheme, like Western numbering, the Long Count days were tallied in a base-20 and base-18 scheme. Thus 0.0.0.1.5 is equal to 25, and 0.0.0.2.0 is equal to 40. The Long Count is not consistently base-20, however, since the second digit from the right rolls over to zero when it reaches 18. Thus 0.0.1.0.0 does not represent 400 days, but rather only 360 days.
... about as much as it does when you took down your 2011 calendar and put up your 2012 calendar. (Or, if you are like me, you realized that you still had a 2008 wall calendar and you replaced that one with a new 2012 calendar.) Or, if you believe in the writings of the Popol Vuh, this date holds some level of significance (but only in that it is the start of the 14th b'ak'tun in 2012, and it took as many b'ak'tuns for the gods to get it right in the first case):
According to the Popol Vuh, a book compiling details of creation accounts known to the K'iche' Maya of the Colonial-era highlands, we are living in the fourth world. The Popol Vuh describes the first three creations that the gods failed in making and the creation of the successful fourth world where men were placed. In the Maya Long Count, the previous creation ended at the start of a 14th b'ak'tun.Of course, all this requires that you also believe that the Mayan gods (or the gods that the Mayans came to worship) are somehow going to come back and re-make the world at the end of 2012. If you believe in another set of gods, believing that the end of the world will occur on December 20, 2012 seems to me to make you at least somewhat accepting of gods that don't belong in your theism. (Whether this is equivalent to apostasy is up to you or your religion, though.) If you don't believe in any set of gods, then this is just a bunch of bunkum. And if you do believe in the Mayan gods, then this is problematic... or is it?
After all, there isn't any actual written prophesy that the Mayan gods will wipe away what took them 14 b'ak'tuns to create in the first place, just that it took them 14 b'ak'tuns to get to man, and that we are approaching the 14th since then.
... so enjoy the year and all the movies that are likely to be released this year about the end of the world. Also, if you feel something that isn't quite right - an earthquake, a tornado, a late snowfall, an early snowfall, a hotter-than-usual summer, etc - then just remember that randomness exists in the universe, and also that we tend to exaggerate and remember events that our minds have been primed to think of as important.
ERRATA: The Mayan calendar's date for the creation of humanity is at odds with Bishop Ussher's calculation of Sunday (had to be a Sunday), October 23, 4004 BC (according to the proleptic Julian calendar). The fact that the two estimates are 890 years apart (give or take some months) probably won't make a difference to YACs who also are using the Mayan calendar to date the end of the world.
UPDATE (2012-02-16): C.G.P. Grey made a video on this topic: