Per app's post, my 2 cents is that the Mayan calendar ends on 2012 because no one really knows when the correct date is and it has been modified time and time again with 2012 being the latest number.
Not that for some reason I kind of feel like 2012 is the correct date but I think even if you love the occult, two things need to be emphasized:
1) Just because a cycle ends doesn't mean a cycle begins. Even if it were to "reboot", doesn't mean we would understand how it would reboot as outside of the little Ice Age, we haven't discovered what a post-reboot environment is really like.
2) Just because a cycle ends, doesn't mean a cycle immediately ends. For all you guys know, the very reason our world was destined to end in 2012 was because everybody was all "Bird Flu", "Rapture" or "Y2K" all about it and when nothing "instantaneous" happened most everyone dropped their guards until events deteriorate beyond repair. (Let's say 2012 was our last chance to reduce pollution or population explosion before things totally go to hell for example)
btw not that Listverse is any credible source but for those looking for some more data about the Dark Planet:
This one started life as an archaeological find. A mysterious clay tablet was found in the Middle East years ago, made by the Sumerians (earliest inhabitants of middle east). Upon this tablet was a depiction of something that looked like our solar system; all the planets were there, and all of them were rotating around the sun. But there were 11 celestial bodies. Now we know there are only 9 planets. Maybe one of them was our moon or the recently discovered mini-planet Sedna? But where did the 11th come from? At the same time astronomers were perplexed by a strange force in the outer solar system. It seemed as though the outer planets were being pulled out of their orbit. Something massive must be out there. These combined findings led to the theory of the mysterious planet X.
Planet X is predicted to be 100s of time larger than Earth and to have a massive orbit of about 3,600 years. When it comes through the inner solar system it could cause cataclysmic disaster upon our planet. It is so massive that it could turn our poles upside down, slow down the earth’s rotation or even stop it. If it gets close enough it could even peel the earth’s crust off, or push us into the sun. All bad scenarios.
On December 21, 2012, the solstice sun will align with the dark rift in the Milky Way. The dark rift (Great Rift) is the widest part of the Milky Way and corresponds to the direction of the center of the galaxy. As the alignment occurs, the solstice meridian will align with the crossing point of the ecliptic (the path of the Sun, moon and planets) and the plane of the galaxy, which is called the galactic equator, and pass on the other side. Alignments occur every 36 years, but this alignment is unique. At this time the sun appears to just touch one part of the dark rift that snakes its way along the Galactic Equator.
This is an area of the night sky considered important to Maya cosmology with respect to spiritual rebirth mythology. In some versions, the combined gravity of the galactic black hole and the sun will cause earthquakes, tsunamis, floods or severe weather. In other versions the alignment will cause more esoteric issues, such as a blockage of an undefined type of energy emanating from the black hole, or from the galactic core, or both. Aligning with the rift could cause major disturbances in the orbits of inner planets. Some people believe that this event could place the Earth in danger of being sucked into a black hole at the center of the dark rift in the Milky Way.
There are about 500 active volcanoes in the world. There are three known supervolcanoes in the US, (including Yellowstone), Lake Toba in Indonesia, Taupo in New Zealand and Aira Caldera in Japan. A supervolcano is a volcano capable of producing a volcanic eruption with an eruption radius greater than 240 cubic miles (1,000 cubic kilometers). Supervolcanoes are the most dangerous, with a Volcanic Explosivity Index of 8. This is thousands of times larger than most historic volcanic eruptions. Geologists believe that Yellowstone is the most likely supervolcano to erupt next, as it has been exhibiting signs of unrest, with earthquake swarms, ground deformation and considerable heat and gas emissions.
Earthquakes are the primary indicator that a volcano is about to erupt. The Yellowstone caldera experiences about 1500 measurable earthquakes a year. The last eruption of Yellowstone was 640,000 years ago. If it did erupt, expect half of the USA to be wiped out, and major variations in global climate for many years. Residual volcanic ash in the atmosphere would result in the devastation of world agriculture, severe disruption of food supplies and mass starvation. Yellowstone could emit 2,000 millions of tons of sulphuric acid, and could produce the equivalent of a “nuclear winter”, when the dust and debris from the fallout of a nuclear war block out sunlight for several years, causing worldwide famines.
In August, 2010, NASA reported that there would be a solar storm sometime in 2012. Every 11 years or so, changes in our star’s magnetic field bring on an increase in sunspots, solar flares and coronal mass ejections. The result is a barrage of charged particles hurling toward Earth. A solar storm is a sudden burst of very fast, charged particles from the Sun. It could be the result of a solar flare or a coronal mass ejection (CME) or both. A coronal mass ejection (CME) is a massive burst of solar wind (stream of charged particles ejected from the sun). A solar flare is a sudden eruption of magnetic energy released on the surface of the sun, usually accompanied by bursts of electromagnetic radiation. Ultraviolet and x-ray radiation from solar flares often induce electromagnetic disturbances in the earth’s atmosphere.http://listverse.com...pocalypse-scenarios/http://listverse.com...pocalyptic-theories/
Solar storms would affect power grids, thus losing electricity. The Solar Storm itself would not cause an apocalypse, but it would bring about a sort of domino effect. People would then lose access to their heat/air conditioning, refrigeration, phone service and GPS. Also, drinking water distribution systems could break down in a couple of hours. Normally, a “Faraday Cage” protects the satellite’s internal equipment from external electrical charges, but constant bombardment of charges would cause satellites to break down. There are over 936 operating satellites in space, worth an estimated $200 billion to replace. Magnetic storm currents acting on gas pipelines are known to enhance the rate of corrosion over time, with potentially catastrophic cumulative effects.
As for my own conspiracy theory: I don't see why a black hole doesn't fit the definition of a dark planet. A google search implies many have similar ideas although I haven't read them but still... it sounds like the most likely random event that coincides with a dark planet.