What happens in 2012 about 2012 Dec 21

Dec 31, 2012?

'"The "Christian calendar" is the term traditionally used to designate the calendar commonly in use, although it originated in pre-Christian Rome. This calendar is used by the United States, and most countries in the world." Is this Mayan calendar in sinc with the Julian or Gregorian calendars?

Before Julius Caesar introduced the Julian calendar in 45 B.C.E., the Roman calendar was used. Originally, the year started on March 1st and consisted of only 304 days or 10 months with nothing noted for the winter season.

If the Roman was wrong, the Julian was wrong and the Gregorian makes the mistake of not taking the apocolapse into considertion, what makes the Mayan correct?

Only two things are infinite, the universe and human stupidity, and I'm not sure about the former. - Albert Einstein