1947 | Seven minutes to midnight
The clock first appears on the Bulletin cover as a symbol of nuclear danger.

1949 | Three minutes to midnight
The Soviet Union explodes its first atomic bomb.

1953 | Two minutes to midnight
The United States and the Soviet Union test thermonuclear devices within nine months of one another.

1960 | Seven minutes to midnight
The clock moves in response to the growing public understanding that nuclear weapons made war between the major powers irrational. International
scientific cooperation and efforts to aid poor nations are cited.

1963 | Twelve minutes to midnight
The U.S. and Soviet signing of the Partial Test Ban Treaty “provides the first tangible confirmation of what has been the Bulletin’s conviction in recent years—that a new cohesive force has entered the interplay of forces shaping the fate of mankind.”

1968 | Seven minutes to midnight
France and China acquire nuclear weapons; wars rage in the Middle East, the Indian subcontinent, and Vietnam; world military spending increases while development funds shrink.

1969 | Ten minutes to midnight
The U.S. Senate ratifies the Nuclear Non-Proliferation Treaty.

1972 | Twelve minutes to midnight
The United States and the Soviet Union sign the first Strategic Arms Limitation Treaty (SALT I) and the Anti-Ballistic Missile Treaty; progress toward SALT II is anticipated.

1974 | Nine minutes to midnight
SALT talks reach an impasse; India develops a nuclear weapon. “We find policy-makers on both sides increasingly ensnared, frustrated, and neutralized by domestic forces having a vested interest in the amassing of strategic forces.”

1980 | Seven minutes to midnight
The deadlock in U.S.-Soviet arms talks continues; nationalistic wars and terrorist actions increase; the gulf between rich and poor nations grows wider.

1981 | Four minutes to midnight
Both superpowers develop more weapons for fighting a nuclear war. Terrorist actions, repression of human rights, and conflicts in Afghanistan, Poland, and South Africa add to world tension.

1984 | Three minutes to midnight
The arms race accelerates. “Arms control negotiations have been reduced to a species of propaganda. . . . The blunt simplicities of force threaten to displace any other form of discourse between the superpowers.”

1988 | Six minutes to midnight
The United States and the Soviet Union sign a treaty to eliminate intermediate-range nuclear forces (INF); superpower relations improve; more nations actively oppose nuclear weapons.

1990 | Ten minutes to midnight
The clock, redesigned in 1989, reflects democratic movements in Eastern Europe, which shatter the myth of monolithic communism; the Cold War ends.

1991 | Seventeen minutes to midnight
The United States and the Soviet Union sign the long-stalled Strategic Arms Reduction Treaty (START) and announce further unilateral cuts in tactical and strategic nuclear weapons.

1995 | Fourteen minutes to midnight
Further arms reductions are stalled while global military spending continues at Cold War levels. Nuclear “leakage” from poorly guarded former Soviet facilities is recognized as a growing risk.

1998 | Nine minutes to midnight
India and Pakistan “go public” with nuclear tests. The United States and Russia can’t agree on further deep reductions in their stockpiles.