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The 2012 date is just the Mayans. Rather than numbers, their calendar was based on their alphabet. Roughly speaking, the first year was like AAAA, the second AAAB, and so on, until you get to ZZZZ. When the alphabet runs out, there are just no more letters to use. Kind of like an ancient "Y2K" bug - and we all now what a threat that turned out to be.