- 1949 – The Soviet Union tests its first atomic bomb. Clock changed to three minutes to midnight – four minutes closer to midnight.
- 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.
- 1960 – In response to a perception of increased scientific cooperation & public understanding of the dangers of nuclear weapons, clock is changed to seven minutes to midnight – five minutes further from midnight.
- 1963 – The United States and Soviet Union sign the Partial Test Ban Treaty, limiting atmospheric nuclear testing. Clock changed to twelve minutes to midnight – another 5 minutes further.
- 1968 – France and China acquire and test nuclear weapons – 1960 and 1964 respectively – wars rage on in the Middle East, Indian subcontinent, & Vietnam. Clock changed to seven minutes to midnight – five minutes closer to midnight.
- 1969 – The U.S. Senate ratifies the Nuclear Non-Proliferation Treaty. Clock changed to ten minutes to midnight – three minutes further from midnight.
- 1972 – The United States & the Soviet Union sign the SALT I – Strategic Arms Limitation Treaty) and the Anti-Ballistic Missile Treaty. Clock changed to twelve minutes to midnight – 2 minutes further.
- 1974 – India tests a nuclear device – Smiling Buddha – SALT II talks stall. Clock changed to nine minutes to midnight – three minutes closer to midnight.
- 1980 – Further deadlock in US-USSR talks, increase in nationalist wars & terrorist actions. Clock changed to seven minutes to midnight – two minutes closer.
- 1981 – Arms race escalates, conflicts in Afghanistan, South Africa, and Poland. Clock changed to four minutes to midnight – three minutes closer.
- 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.
- 1988 – The U.S. and the Soviet Union sign treaty to eliminate intermediate-range nuclear forces, relations improve. Clock changed to six minutes to midnight – three minutes further from midnight.
- 1990 – Fall of the Berlin Wall, success of anti-communist movements in Eastern Europe, Cold War nearing an end. Clock changed to ten minutes to midnight – 4 minutes further.
- 1991 – United States and Soviet Union sign the Strategic Arms Reduction Treaty. Clock changed to seventeen minutes to midnight – seven minutes further, its greatest distance from midnight so far.
- 1995 – Global military spending continues at Cold War levels; concerns about post-Soviet nuclear proliferation of weapons and brainpower. Clock changed to fourteen minutes to midnight – three minutes closer to midnight.
- 1998 – Both India and Pakistan test nuclear weapons in a tit-for-tat show of aggression; the United States and Russia run into difficulties in further reducing stockpiles. Clock changed to 9 minutes to midnight – five minutes closer.
- 2002 – Little progress on global nuclear disarmament; United States rejects a series of arms control treaties and announces its intentions to withdraw from the Anti-Ballistic Missile Treaty; terrorists seek to acquire nuclear weapons. Clock changed to seven minutes to midnight – two minutes closer.
