What is it about?
The general idea that bad stuff is going to happen on December 21, 2012, comes from a Maya calendar. The Maya "Long Count" calendar uses various units of time to make up different cycles. Apparently the Mayas were big on cycles, as the excerpt from wikipedia (below) indicates.
"20 days made a uinal, 18 uinals (360 days) made a tun, 20 tuns made a k'atun, and 20 k'atuns (144,000 days or roughly 394 years) made up a b'ak'tun."
Now, according to a Maya text called the Popol Vuh, the gods created 3 worlds before ours, all of which failed because the basic inhabitants lacked speech, soul or intellect (the first 3 worlds being centred around animals, mud men and wooden men, respectively). Anyway, the source of the whole Maya 2012 thing lies here: the world before ours (world #3) lasted 13 b'ak'tuns, or around 5,125 years, before being remade into our world (world #4). According to interpretations of the Maya calendar, 2012 marks the 13th b'ak'tunniversary of our world. So basically, because legend tells that the gods decided, after 5,125 years, that they'd rather have a world of cornmeal-dough men (yep, the myths say we were made out of corn meal) than their current world of wooden men, various people are concluding that this means we're about to reach the end of our earthly lease.
Recently, a lot of people have been jumping onto this date, usually claiming to back it up with science or other prophecies. But as a starting point, does this sound like a reasonable interpretation to you?
More to come...