Why the attention on December 21?
That’s where the disagreements start. Some of the people who study the Mayan calendar say that’s the day the current cycle will end. Others say picking the exact day is more problematic, given a diversity of opinion even among the Maya about the exact dates of the calendar. December 21 happens to be the date of next year’s winter solstice, which is a big deal for many of the 2012-ers. And it’s also tied to another real astronomical event: The earth and sun will be roughly lined up with the center of the Milky Way galaxy.
