There has been some ballyhooing about the supposed Ancient Mayan calendar ending on December 21, 2012. There are at least two Hollyweird blockbusters coming out about the world ending in catastrophic disasters and what not. How quickly we forgot the end of the world bust that was Y2K.
There is a fabulous article in the current edition of Archaeology Magazine, which can be found online here. For those wanting resources to reassure people that the world will not in fact end then, I highly recommend reading this article.
For those interested in how the ancient Mayan calendar works, let me explain the math behind it. The Mayan calendar is basically 5125.37 of what we would consider years of the normative Gregorian calendar. That number might seem random to us, but it actually makes sense if you understand the Mayan counting system, referred to in the article above as the Long Count. This is basically a base-20 system.
The primary time unit being a kin, or day.
A Uinal is a Maya month of 20 days.
A Tun is a Mayan year, or 18 Uinals (360 days).
A KaTun is 20 Tuns or 20 Mayan years (7,200 days).
A BakTun is 20 Katuns or 400 Mayan years (144,000 days)
Thus, were we might have a date that looks like this: 09.12.09. Mayan calendar date inscriptions would look something like 18.104.22.168.3 (For those scoring at home, that would be January 1 of the Year Zero on our calendar.) Thus, to read a Mayan calendar as such, that would be the 7th day of the 17th Month of the 18th Year of the 13th 2-decade cycle of the 3rd 400-year cycle from the beginning of the Mayan calendar is 3114 BC.
Now, that may be clear as porridge, but as this article above surmises (and I think correctly), the date the Mayans chose to begin their calendar (the year 3114 BC) was completely arbitrary. There were no astronomical events of that year, and in fact, the Mayan culture had not even come into existence yet. The earliest Mayan calendar inscriptions were not until around 230 BC. The Mayans probably started their calendar on a date based on some oral history now lost to antiquity, probably in the same way we might try to determine when Abraham or King Arthur might have lived, i.e. ballpark figures at best. Read the article for further archaeological suppositions on that.
I noted with interest in the article that archaeologists have noted that the Maya had no central belief in common on what would happen after the calendar in essence reverted back to zero. Some cities predicted happily ever after ending, some predicted dread disasters, and others seemed not to have been concerned at all.
In other words, the more things change, the more they stay the same. People freaked out when the Christian calendar turned over to the year 2000, and nothing happened. 2000 is just the logical number that follows 1999. Likewise, the way the Mayan calendar was set up on the base-20 system, eventually it was going to have to reset itself, much like old odometers in cars will eventually (assuming the car lives long enough) roll back over to 000,000 after going one mile over 999,999 miles. There just simply is not a 7th digit, and it has to reset itself.
In sort, don't get freaked out by all this stuff. It's just Y2K all over again. The only difference this time around is a lot of extra hocus pocus Mayan mysticism, most of which is not even authentically Mayan, but Dan Brown type fiction and conspiracy theories.