Let me see if I can word it correctly.

AFAIK, the Mayan calendar years were not numbered 0 (or 1) to 2012. The Mayan calandar was a set of divisions that accurately accounted for days and years based on the earth's orbit around the sun (like the Gregorian calender we use today).

For all I know, the start of each Mayan year might have been April 23rd on our calendars. I don't know how the years were broken down other than by number of days. But it's not important, because we don't talk about the Mayan calendar in terms of Mayan dates. We talk about the Mayan calendar in terms of Gergorian dates.

The year that Christ was born compared to the year we based our calendar on has no bearing on how we describe the calendar in our terms.

Another way to look at it is this: when they looked at the calander, instead of thinking in terms of years, think in terms of days. They didn't just look at the calendar and say, "It says it stops in 2012". They said "There's 1000 days left on this calender. In 1000 days it will be 2012. This calendar ends in 2012" (obviously it was more than 1000). It really doesn't matter when we started counting years on our calender, the Mayan calender ends 1000 days later relative to ours. So unless our calender changes sometimes between when we discover it and when it ends, the result will always be the same.

Ergo, the Mayan calendar ends in OUR year 2012.

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I'm like one of those idiot savants...well, except for the savant part.

Theory of Zombie Relativity:
1) Everyone Else is a Zombie relative to You
2) Whether or not it matters is related to the inverse square of the distance between their teeth and your brain
(Quoted from Demigrog)