The Doomsday Clock was last moved on February 27, 2002 and currently stands at seven minutes to midnight.
I think the clock only moves closer to midnight when the Bulletin decides that the US is endangering the world. Apparently, Korea is not worrying them.
The worst it has been is 2 minutes to midnight, I have heard. There was an Iron Maiden song about it call, you guessed it, "2 Minutes To Midnight."
I just found it.
1953 - The United States and the Soviet Union test thermonuclear devices within nine months of one another. Clock changed to two minutes to midnight (one minute closer, its closest approach to midnight to date).
1984 - Further escalation of the arms race under the U.S. policies of Ronald Reagan. Clock changed to three minutes to midnight (one more minute closer).
You can see all the changes here:
http://en.wikipedia.org/wiki/Doomsday_clock