On the night of September 26, 1983, a nuclear war nearly began between the USSR and the USA. This is because the systems in Serpukhov near Moscow notified the launch of intercontinental missiles launched by the United States towards the Soviet Union.
Lt. Col. Stanislav Petrov did not let that happen.
September 26 is International Day for the Total Elimination of Nuclear Weapons. This day was established by the UN General Assembly on December 5, 2013.