When did the first-ever treaty banning nuclear weapons come to force?

The Treaty on the Prohibition of Nuclear Weapons is the first-ever treaty to ban nuclear weapons. It entered into force on 22^nd January 2021 with an aim to get rid of nuclear weapons. It was approved by the UN General Assembly in July 2017. It was opposed by all nuclear-armed states as well as the 30-member NATO. Japan, the only country where nuclear attacks took place, also did not support this treaty.