International days are observed by the United Nations as occasions to mark particular events or topics in order to promote, through awareness and action, the objectives of the United Nations. Usually, it is one or more member states that propose these observances and the General Assembly establishes them with a resolution.

International days are sometimes commemorated with high-level meetings. There are various high-level meetings Reaching Critical Will has monitored over the years: the International Day for the Total Elimination of Nuclear Weapons, the International Day against Nuclear Tests, the high-level meeting on nuclear disarmament, and the high-level meeting on nuclear safety and security.