Do you remember the so-called "millenium bug"? Because of the two digit representations of the year on our computers nobody knew for sure what was going to happen when 12-31-"99 turned the next day 1-1-"00?
That thing was covered on television and in the newspapers relentlessly as the "Y2K Bug". Warnings that your electricity, telephones, and other utilities might be rendered useless were everywhere. People rushed to the grocery store and stocked up. Folks loaded their guns waiting for the looting to begin.
Guess what I did.....I bought two tickets to the nicest dinner and concert venue in town, booked a 5-star downtown hotel, and took my wife out for the best New Years Eve date ever. The streets were emptier than I had ever seen them before on New Years, and that meant no waiting. The next afternoon when we arrived back at our house, the light switch worked, the telephone had messages on it, and my computer fired up like normal.
The short answer to your question; no, the world won't end on 12-21-2012, but I do believe someday man will destroy the planet. Stocking up on groceries will make little difference though, when that day comes it's just over. The best advice is to live your life like everyrday could be the last.