When is the World coming to an end?

Science demonstrates that the World is imminently coming to an end. The problem is that we don't know the exact reason nor the time that will lead this world to its Apocalypse.
The Sun that is the source of life on Earth is probably the one who will end it when it will run out of its internal fuel, it will cool down and it will expand till it swallows all the planets surrounding the Sun. For this to happen, it will take a minimum of a billion years (if my calculus is right).
We are living in a Universe full of uncertainties, and since the down of time, the scientists were haunted by this question, and the answer was never that obvious. All that they can do is to provide a description of the possible scenarii. Some religions and the lore are providing some details about how this will be happening and sometimes when, again the problem is the interpretation of scholars that we cannot trust all the time ( as it was the case for the Mayan prophecy). May be in the newt years we will have more data to counter all these uncertainties about our existence.