Despite what you might believe from watching movies such as Deep Impact or Armageddon, we're not likely to have months or a year to prepare to take a catastrophic meteor impact.
As this story relates: http://www.breitbart.com/article.php?id=CNG.783c3aae6eb418393fc6f8c443ef6765.2f1&show_article=1
a sizable rock just flew by us this weekend.
If it had hit it would have been as big a blast as the famous 1908 event that flattened a Siberian forest. Now, the Earth is a big place and it's more likely than not that something like that would end up exploding over the ocean, a pole, the Sahara or Himalayas or Siberia again and not over India, coastal China, Paris or New York --but do we feel that lucky?
The story said that the rock flew by Monday and had been detected only Saturday! This suggests that, given the time needed to calculate trajectories and get the word out, average people would have had, at best, a little more than a day to get ready.