The General Assembly, in its resolution A/RES/65/271 of 7 April 2011, declared 12 April as the International Day of Human Space Flight “to celebrate each year at the international level the beginning of the space era for mankind, reaffirming the important contribution of space science and technology in achieving sustainable development goals and increasing the well-being of States and peoples, as well as ensuring the realization of their aspiration to maintain outer space for peaceful purposes.”

12 April 1961 was the date of the first human space flight, carried out by Yuri Gagarin, a Soviet citizen. This historic event opened the way for space exploration for the benefit of all humanity.

The General Assembly expressed its deep conviction of the common interest of mankind in promoting and expanding the exploration and use of outer space, as the province of all mankind, for peaceful purposes and in continuing efforts to extend to all States the benefits derived there from.

On 4 October 1957 the first human-made Earth satellite Sputnik I was launched into outer space, thus opening the way for space exploration. On 12 April 1961, Yuri Gagarin became the first human to orbit the Earth, opening a new chapter of human endeavour in outer space.

The Declaration further recalls “the amazing history of human presence in outer space and the remarkable achievements since the first human spaceflight, in particular Valentina Tereshkova becoming the first woman to orbit the Earth on 16 June 1963, Neil Armstrong becoming the first human to set foot upon the surface of the Moon on 20 July 1969, and the docking of the Apollo and Soyuz spacecrafts on 17 July 1975, being the first international human mission in space, and recall that for the past decade humanity has maintained a multinational permanent human presence in outer space aboard the International Space Station.”

https://www.un.org/en/observances/human-spaceflight-day