Hopfully the following should calm your worries about this.
It's all to do with the Mayan Calender.
The Maya were a clever bunch of folks. Their civilization got started several thousand years ago and reached its height by 900 A.D., spread over the Yucatan Peninsula in present-day Mexico. They had a sophisticated culture and were adept in agriculture and architecture. They had a complex written language and a keen system of mathematics. They were excellent astronomers, understanding the patterns of the stars and planets in the sky. And, of course, they had an advanced calendar. Several, in fact.
Keeping time is of paramount importance to any civilization. The Maya used different calendars for different purposes (we do too; there are fiscal calendars and monthly calendars and others that are arbitrary and headache-inducing, so don’t be too hard on the Maya). The calendar we’re interested in here is called the Long Count.
It had as its basic units a day (called a k’in) and a 360-day period called a tun. The Maya understood that a physical year was five days longer than a tun, and had other calendars to deal with that. They had longer units, too, like the ka’tun—just shy of 20 years—and most importantly for apocalypse aficionados, the b’ak’tun—roughly 394 of our years. The starting point for their calendar (Year Zero, if you like) is 3114 B.C., the date they figured the Earth was created.
Knowing all this, we can match their calendar to ours and convert any date they used to our more familiar system. If you do the math, you’ll find that we are nearing the end of the 13th b’ak’tun. In fact, it ends on Dec. 21, 2012.
That’s this Friday. Cue the spooky music.
The thing is, there is no suggestion, not even a hint, in Maya writing that they thought the end of this current b’ak’tun had any connection to doomsday. It’s entirely possible it may have even been thought of as a time of celebration (just like we celebrate New Year’s Eve).
The Maya also had bigger units of time, including the piktun (which was either 13 or 20b’ak’tun), and the alautun, which was—get this—63 million years! So it doesn’t sound like they were predicting the end of the world ever, let alone by this weekend.
Anyway, it hardly matters. Just like our calendar, theirs was based on cycles. At the end on a cycle, you reset all the current units and move the biggest one up a notch. It’s what we do on December 31: Reset to the first day of the first month, and increment the year by one. Happy New Year! Same thing with the Long Count. After the last day of the 13thb’ak’tun, they’d start over at the next one.