2012 is an interesting date. The Mayan calendar is the most accurate calendar ever developed by man. The Mayan calendar ends in 2012. Date setting is dangerous, as many cults have discovered to their embarrassment.
However, if you date the rebirth of Israel as one of the last signs add 70 to 80 years (Psalm 90:10) as the length of a generation then 2012 falls within the that span of time. As to a comet or asteroid hitting the earth being part of God’s plan the optimal place for it to strike is the Pacific Ocean where most of earths islands are located.
Rev 8:8-12
8 And the second angel sounded, and something like a great mountain burning with fire was thrown into the sea; and a third of the sea became blood; 9 and a third of the creatures, which were in the sea and had life, died; and a third of the ships were destroyed.
10 And the third angel sounded, and a great star fell from heaven, burning like a torch, and it fell on a third of the rivers and on the springs of waters; 11 and the name of the star is called Wormwood; and a third of the waters became wormwood; and many men died from the waters, because they were made bitter.
12 And the fourth angel sounded, and a third of the sun and a third of the moon and a third of the stars were smitten, so that a third of them might be darkened and the day might not shine for a third of it, and the night in the same way. NAS