We already have been claimed to be doomed a gazillion times.
The Maya's are just laughing their skeletal asses off in their graves from trolling the modern people.
They where just to lazy to finish that stupid calender.
Sorry, meant to hit quote.
Anyways...
The point of the Doomsday Clock isn't to literally say, "We're x minutes away from the apocalypse!" It's meant to convey, through a handy visual metaphor, how close we are (or at least, could be) as to catastrophic devastation. Considering recent events (Iran's advancing nuclear efforts and beilligerent threats, the recent regime change in unstable North Korea, continuing ecological damage, etc.), the reasoning behind moving the minute up is perfectly reasonable.