When is the world ending but not twenty-twelve?

Answer 1

Depends on what you mean by world.

Life on this planet will end in about one billion years (That's, 1,000,000,000 years) so plenty of time to do stuff, raise a family and have a glorious life.

In about a billion years, the Suns temperature would have increased so much that all liquid water on the planet would have evaporated into space.

The planet Earth, will survive for eternity.

Much has been said about the Sun becoming a red giant and enveloping the Earth, however, in the red giant stage, the Sun would have lost so much mass, that the Earth will migrate away from the giant fire ball that will occur.

After than, when the Sun becomes a white dwarf, the Earth will just be a cold rocky planet with zero life.