In LOST, the end of the world is predicted by the Valenzetti equation. The equation was developed shortly after the Cuban Missile crises and Alvar Hanso funded the Dharma Initiative to try and change the core coefficients of the equation which represents human and environmental factors. Not coincidently the coefficients are 4, 8, 15, 16, 23, 42 which are also the mysterious numbers seen on the Swan hatch door and entered into the computer there, and were transmitted from the radio tower which led Danielle Rousseau and her science crew to the island. Hurley also discovered the numbers (and foolishly used them to win the lottery) through his friend Leonard who he met at the mental institution. Unfortunately the result of the Valenzetti equation is shrouded in mystery. Valenzetti died under mysterious circumstances and Gary Troup who investigated his research also died as a survivor of Flight 815, was sucked into the engine that exploded on the beach.
So no one knows what the year of Doomsday or Armageddon is by using the Valenzetti equation. But the new movie 2012 proffers a new theory. The end of the world will occur on 12-21-12 as predicted by the Mayan calendar it is said. The Mayans (using the stars and astronomy) calculated different cycles when the earth would align with the sun, moon and the core of the Milky way galaxy causing the earth’s core to heat up and displace the earth’s crust causing volcanoes, earthquakes and tsunami’s.
According to this Wikipedia article the Mayan’s are being used to shamelessly promote Western theories and stories and they put little emphasis on what would actually happen in 2012.
From a science fiction standpoint my guess is that LOST is describing an end world scenario based on what we humans (do) or don’t do and that leads to the extinction of humanity, whereas in 2012, what happens is out of our control. What side do you fall on? Will we decide our own fate or will it be decided for us?