The world has become a safer place for the first time in nearly 20 years. Or at least that’s the message from the people behind the Doomsday Clock.

The clock is a project run by staff at the University of Chicago’s Bulletin of the Atomic Scientists. It aims to symbolize changes in world security through the metaphor of midnight being the moment of world destruction. It began in 1947 at 11:53pm and has now been adjusted 19 times. The clock image appears on the front cover of each issue of the bulletin with its current setting.

Most adjustments have been based around the availability of nuclear weapons and the state of relations between the major global powers. The latest the clock has ever reached was 11:58  in 1953 after the US and Soviet Union both tested thermonuclear devices, while the earliest was 11:43 in 1991 when, following the end of the Cold War, the two nations signed the Strategic Arms Reduction Treaty.

Since that time the clock has moved consistently forwards, thanks mainly to more nations developing nuclear weapons and the risk of nuclear material getting into the hands of terrorists. Three years ago, the dangers of climate change were taken into account for the first time.

The staff has now decided to move the clock back one minute to 11:54, stressing that though things were moving in the right direction, the changes were minimal. They said factors influencing the change included better international collaboration on limiting nuclear weapons and wider acceptance of the need to tackle climate change.

(And now a question for GeeksAreSexy readers: does anyone know why the clock was originally set at 11:53pm? My best guess would be that it derives from metaphors about human life’s arrival time if the history of Earth was condensed to 24 hours, but I’ve been unable to confirm this.)