If I had to choose any single day when the world will end within our lifetime, I'd have to go with April 13, 2029 at 15:46 CDT (give or take a minute).
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That's when asteroid "99942 Apophis" will pass by Earth at a distance of 18,600 miles. That's assuming its orbit and Earth's orbit doesn't change by then. A collision with another asteroid between now and then could knock 99942 Apophis into a closer (or further) orbit.
99942 Apophis is 1300 feet in diameter and will be travelling at 16,695 mph. Its magnitude (brightness) will be "3" as it passes by, making it visible to the naked eye. If it skims the upper layers of the atmosphere, it will look like this: <A HREF="http://www.zjstech.net/~library/4249/tetonmeteor.mpeg"> LINK </A>
On April 13, 2029, we'll have a very bright, large full moon that will be 221,739 miles away from Earth.
The link below shows how close it'll be. Click DATE (a date box opens). Enter "April 12, 2029." Choose "Earth" as the center. Zoom in all the way. Use the sliders on the bottom and right side of the picture.