I am an astro physicist with a minor in astrology. Don't buy that shit. In the mid 90's a lady running a website claimed that ET's told her telepathically that Nibiru would collide with us. That is the first known source of the rumor. Nibiru has been talked about for a long time and does exist (and there are probably many more planets orbiting our sun beyond it), but it is certainly not trying to kill us.
Nibiru or planet X lies outside of pluto which is on average about 370 million miles away from Earth. The stars and planets are like grains of sand separated by miles. It is so incredibly unlikely for a planet that far away to drop it's orbit and come racing toward Earth with such exact precision. It just won't happen, don't worry about it. I'm also an avid researcher of the ancient world, and the Mayan calendar is blown way out of proportion. They never claimed the end of the world. They, being brilliant mathematicians and astrologists, calculated that the Earth's wobble is on a precessional cycle of about 26,000 years, which they split into 5 "times" of 5,125 years- the long count calendar. At the end of each of these "worlds", so to speak, they have stories of the Earth cleansing itself. They say that the last was a great flood and sea levels rising. This year, it is the year of the jaguar, and the story tells of great earthquakes. I guess it's very possible that the earth's wobble has a major effect on world climate, but any change will be gradual. all the other BS you hear on the subject is just that... BS made up by scum to make money from web advertising on their propaganda doused websites. I don't mean to sound like a know it all, but I've been researching the mayan in depth for a decade, as I used to want to be an archaeologist, and i definitely do know this subject in and out.
The internet is a great resource, but it can be hard to separate facts. You can PM me if you are interested to know any details or specifics.