International Intelligence Day takes place on October 1st every year, and Mensa International and national Mensas organize diverse activities to commemorate the establishment of Mensa in 1946.
Mensa was founded in Oxford on 1 October 1946 by the eccentric Australian Roland Berrill (1897–1962), a former English-educated lawyer who never practiced law but made a living from his investments, and the reserved Englishman Dr Lancelot Lionel Ware (1915–2000), then a student at Oxford who later achieved several academic degrees in science and law. They met by chance on a train. Ware is credited with the idea of Mensa, but it was Berrill who "founded" the society in it's usual form. At the very beginning, Berrill provided the initial funds, defined the rules, became Mensa's first secretary, and, by conducting IQ tests, recruited a total of around 400 people. However, he died a few years later. Dr. Lancelot Ware left Mensa for a short period of time, but re-joined and remained a member until his death in 2000, insisting on the original idea being his own.
The celebration of the first International Intelligence Day was first initiated by the German Mensa in 2010, and the same year, the Mensa Croatia joined, along with 18 national Mensas from four continents. Intelligence Day brings attention to the identification of intelligent, gifted, and creative individuals. National Mensas worldwide have a practice of organizing various activities: webinars, conferences, workshops, public lectures, etc. Mensa Croatia, which participates in the campaign every year, has conducted various activities over the years, such as lectures, workshops for gifted children and various gatherings. On the occasion of Intelligence Day, Mensa Croatia, in addition to testing sessions, also organizes an annual gathering of members, each year at a different location.
