Julius Caesar created the concept of a “leap Year” in 45 B.C. – where as every year in multiples of 4 there’s an extra day added. This concept was not inherent in the 1 calendar that everyone is fixated on of the 12 or so Mayan calendars that exists. Since 45 B.C. there has been 513 leap years – which means our Gregorian calendar is actually 513 days behind where the Mayan calendar would be.
According to the Mayan calendar it’s actually some time in 2014. The Mayan 12/21/12 came and went around 510 days ago.