This theory is because of a set of religiuos misinterpertations.
First of all, the age of the world is split up into twelve sections, or twelve "ages". we are currently in the age of Pisces. This is also known as the age of Jesus in Biblical terms. When the end of this age comes, there will be the dawn of a new age, the age of Aquarius. In the Bible (New Testament?), there is a typo, where Jesus says "I will follow you until the end of this world", where he was referring to 2012, when the ages transfer from the age of Pisces (Jesus) to the age of Aquarius (Andrew and Paul, I think). What is was meant to say, was "I will follow you to the end of this age".
Most religions/cultures follow this timeline of ages, and a lot of their cultures/religions, for whatever reasons, also saw this changing of ages as the end of the world.
And so he said, "and there will be delicious cake", and with those words, I said, "I see what you did there..."