End of World myths are as old as civilization. When people don't have to worry about their daily survival any more, they start to think and make up weird things.

http://www.bible.ca/pre-date-setters.htm

On the day of the spring equinox the zodiac constellation where the sun rises marks the era. An era lasts a bit longer than 2000 years. The sun goes backwards through the zodiac, and the time it takes to pass all zodiac signs (about 22000 years) is called the Great Year. The Mayans too could have been aware of this, and 2012 their Great Year could simply end, because they use a different zodiac than the cultures originating from the middle east.
The bible mentions a range of four eras. Taurus lasted until Moses appeared, that's why he dismissed the golden calf (Taurus). The era after Taurus was Aries, and Jesus marks the beginning of the era of Pisces (that's why the symbol of Jesus is the fish). The New Testament also states that after Jesus, there will come a man carrying water (Aquarius). But nobody of us will live long enough to witness the dawn of Aquarius.

http://en.wikipedia.org/wiki/Age_of_Aquarius