There is a clock at the University of Chicago called the Doomsday Clock whose time perpetually lingers just shy of midnight. On this clock, midnight metaphorically represents full nuclear war bringing an end to all civilization, and the clock is meant as a gauge to constantly indicate humankind's proximity to this horrific event.
When it was introduced in 1947, it was set for seven minutes to midnight. Since that day, its minute hand has wandered around on the upper-left quarter of the clock face, inching closer to 12:00 when the threat of nuclear war grows, and crawling away as the risk fades. It has been as close as two minutes to midnight in 1953, and as far as seventeen minutes in 1991. If its caretakers ever set it for midnight, it will probably be the last thing they ever do.
The custodians of this clock have been the men and women of the Board of Directors of the Bulletin of the Atomic Scientists. The Bulletin is a publication which was founded in 1945 by many former Manhattan Project physicists, and over the years contributors have included Albert Einstein, Edward Teller, J. Robert Oppenheimer, Carl Sagan, Wernher von Braun, Al Gore, Isaac Asimov, and Arthur C. Clarke to name but a few.
Today it stands at seven minutes to the hour. Whenever you're curious how near humanity is to destroying itself, you can check the status on the Doomsday Clock homepage. It's good to stay abreast of this sort of thing so you can plan your schedule around it.