Remember all that talk about the world ending in 2012? Yeah, the world and we are still here, so we know that didn't happen. The Maya knew it wouldn't happen either. Let me explain their calendar system, so you have a better idea of what I am talking about.
Be warned that the calendar systems are complicated and there's a lot of information.
The Maya used two calendars: the 260 day ritual calendar known as the Tzolk'in and the 365 day solar calendar known as the Jaab' or Haab.
The 365 day solar calendar had 18 months that was 20 days long. The 19th month, known as the Wayeb, was considered unlucky, because it was only five days long.
The 260 day ritual calendar was used for naming and divination. The numbers 1 through 13 were coefficients for 20 day names.
When the two calendar systems (Tzolk'in and the Jaab') were combined, the system is known as the Calendar Round. Every day of the calendar is a combination of the two calendar systems. It would take 52 years for the two calendars to match back up again within the calendar round (i.e. it would take 52 years for the specific day K'an 1 Pop to happen again). This calendar system is cyclical.
The Classic Maya developed a third calendar system called the Long Count, which counted back from a fixed point in time (the beginning of creation or approximately August 13, 3114 B.C.E. or 13.0.0.0.0 4 Ajaw 8 K’umk’u. ). The Long Count is linear and continuous. One Great Cycle may end, but another Great Cycle always begins. This is the system that the 2012 stuff refers to. The 13th Great Cycle ends December 21, 2012 (depending on your interpretation). The 14th Great Cycle ends March 26, 2407. The 15th Great Cycle ends June 28, 2801. So yeah, it keeps going (I'm not going to list any more Great Cycles, because well... there is no stopping point and I don't want to write a continuous, never-ending list) and would have been considered a momentous occasion.
Okay, the next bit is more complicated, but try to refer to the picture.
That image is a Maya long count calendar date. The initial series introducing glyph (the first one right at top that takes up both slots A and B) signals that a long count date is about to begin. It is read left to right, two columns at a time.
(Second Row) The glyph on the left is a Baktun. The glyph on the right is a Katun.
(Third Row) The glyph on the left is a Tun. The glyph on the right is a Uinal.
(Fourth Row) The glyph on the left is a Kin. The glyph on the right refers to a day from the ritual calendar.
(Fifth Row) The first and second glyph (right and left) refer to a Lord of the Night title.
(Sixth Row) The first and second glyph (right and left) refer to a Lunar series.
(Seventh Row) The glyph on the left refers to a Lunar series. The glyph on the right refers to the day from the solar calendar.
Now you know how to read the basics of a long count calendar date!
You know how contemporary calendars 'end' each year, but a new one begins? (2015 recently ended, but 2016 started) That's what the Maya were essentially talking about, not the end of the world.
Now, I am going to teach you a little bit about how to read a Maya glyph, so you can brag even more.
The Maya counted numbers with dots and bars. The picture above explains their counting system. Each dot represents a count of 1 while each bar represents a count of 5. Go back to the second and third row from the picture of the long count and see if you can read the numbers that are being talked about.
According to Wikipedia, the world was prophesized to end approximately 5 times in 2012.
I can't speak for the accuracy of any other prophesized apocalyptic event, but the hubbub with the Maya Calendar originates from a misinterpretation of the Maya calendar and a misrepresentation of the culture. The popular media capitalized on this, because our attention is easily captivated by ancient cultures and impending doom.
There were actually really big celebrations at many of the largest Maya archaeological sites in Central America in December 2012, because the descendants wanted to celebrate the beginning of a new calendar cycle. It's just like our celebrations during New Years!