Planet X? Wasn't that supposed to be here in the middle of 2003 according to the paranoid schizophrenic who invented it, Nancy Lieder? Perhaps it's late. Perhaps it isn't coming. Perhaps it got discouraged by the fact that almost all the adult population of this planet either had not heard of it or didn't believe in it and decided not to come after all. After all, it would not wish to be an unwelcome guest.
Or maybe it just does not exist.
Isn't Niburu a separate hoax invented by Zacharia Sitchin? Isn't it supposed to be here in 2085 or maybe about 3000? Maybe it does not exist either.
If you want to know about Bible prophecy, ask the battlers in Religion and Spirituality. You will get several different answers there. All I know is that the dozens of prophecies based on Revelation have never happened.
Did the Mayans really predict this? Or was the prediction invented by Jose Arguelles in one of his woo-woo books a few years ago?
What 9 other religions? Do the Sikhs predict this? What about the Hindus? I know a devout member of the Brahmin caste (the one from which all Hindu priests are selected) and she has never said anything.
Which Buddhists say this? Zen? Mahayana?
Do the Jews predict this? The Orthodox? The Reformed? They probably regard Revelation as nonsense.
How about Islam? What do the Shiites say? What about the Sunni?
Do the Roman Catholics, Methodists, Othodox, Presbyterians, Anglicans, Lutherans or any of several other sects have anything to say about 2012?
I suggest you check the veracity of your sources. You may find that some or all of them are liars.
EDIT Now to get really serious, I watched a clip on YouTube a week or so ago. It claimed that archaelogist Layard discovered many cuneiform tablets in 1851. So far, it was correct, apart from getting his name slightly wrong. It then went on to imply that the tablets were Babylonian or Sumerian and also implied, without actually stating, that they were 6000 years old. The reality was that they formed part of the library of a king of Assyria, not Babylon or Sumer. This king was Ashurbanipal, who is very well known to ancient historians, since he was born around 685BC and became king about 668BC, was one of the few literate kings of those times and was known for that. He was also somewhat of a mathematician and was also known for cruelty. The only factual part of that part of the story is that some of the content of some of the texts, for example the Enuma Elish and the Epic of Gilgamesh were indeed very old and long preceeded the Assyrians and Babylonians.
While the Assyrians inherited a good deal of Babylonian culture, and the Babylonians inherited the Sumerian culture, the Assyrians spoke a form of Aramaic, the language commonly spoken in New Testament times. Babylonians spoke Akkadian, which is not closely related. By the time of Ashurbanipal, cunieform writing was all but obsolete since it was complex, but like Egyptian heiroglyphics was considered to be the official or sacred form of script. While the tablets held cunieform script, they would mostly have been in Aramaic, not Akkadian and almost certainly not in Sumerian, since the Sumerian civilisation had all but vanished around 1400 years before.
This video then went on to say that the asteroid belt between Mars and Jupiter was somehow due to the influence of Pluto. At that point I stopped watching since I had seen one minor error, three attempts at disinformation about ancient history and one idiotic lie about the solar system. That was in the first minute and 44 seconds.
The fraud Zecharia Sitchin whom I have already named, pretended after the 1970s to have knowledge of cunieform, which may have been partly true. But he made sure his translations of these old texts conformed to his thesis that Nibiru was inhabited by the beings referred to in the Bible as "giants". To do this he translated texts in one language as if they were in another. These giants were supposed to have created the human race by crossing themselves with apes, the human race was then supposed to be a slave species intended to mine gold for them. This is a version of the old Mesopotamian legend that the gods got tired of working and created humans to do the work instead.
EDIT the second. I have been answering questions on Yahoo Answers on this exact topic for 2 years. Versions of this question have been asked something like 15,000 times. I have actually checked the facts in real books of ancient history and reliable websites and checked out many of the astronomical facts both in books and on reliable websites.
I have seen photon belts, mass earthquakes, planetary alignments, galactic alignments, the "rapture", the I Ching, Revelation, Nostradamus, aliens, planet X, Nibiru, Mayan, Aztec and Incan calendars, changes in consciousness yadda yadda blah blah all advanced by one person or another. Almost everything advanced is based on superstition, frequently refuted assertions, delusion and straight out lies. The people who promote this stuff can't even keep their lies straight.
I have answered this question hundreds of times and I actually do have some idea of what I am writing about. Strangely enough some of the others who regularly answer on Astronomy and Space also actually know what they are writing about.
If they present you with factual answers that do not fit in with your prejudices then I suggest you do not go on about defensive run-arounds and keep your opinions to yourself.