I'm gonna make my own doomsday prophecy. Those jerks don't own doomsday! First I wil go down into my lab and work out the numbers using the Bible, the Mayan calender, the prophecies of Nostradamus, and the Betty Crocker Cookbook. I whip those into a galactically cool number like Apriluary elevety-first 2042. I know what you are thinking, but when I am Exaulted Lord of the Universe I can name the months anything I damn well please! Peon.
So next there needs to be some signs that the end is nigh. First, Skynet needs to go online. The Navy has just developed a laser that will stop a tank or another boat. Not long now.
Second, I will ascend to my rightful place as Master of Earth and it's suburbs. That will fulfill a bunch of prophecies. Antichrist, antibudda, anti-fill in the blank with your favorite god here.
Third. I need a super generic clincher. Like amongst political turmoil a famous person will be usurped.
Done and done. Now to get working on being declared world leader.