Don't be so sure. A lot of writers manipulate the "evidence" of it to support their claims of what's going on or what's going to happen. There's a hell of a lot we don't know about the Mayan civilisation, so there's no way we can even be certain that's what the calendar means. The notion that the apocalypse will strike on that date is very much a New Age spirituality thing, and a lot of mainstream Mayanists - people who have studied the culture and so on - reject it.
For all we know, the Mayans made that calendar to mark the end of a cycle and didn't make another one because it listed a date six hundred years after their culture was destoryed, so they saw no need to begin another because they wouldn't need it for centuries. Then the Spanish came along and conquered South America.