The ENIAC Day

In 1942, physicist John Mauchly proposed an all-electronic calculating machine. The U.S. Army, meanwhile, needed to calculate complex wartime ballistics tables. The result was ENIAC (Electronic Numerical Integrator And Computer), built between 1943 and 1945—the first large-scale computer to run at electronic speed without being slowed by any mechanical parts. For a decade, until a 1955 lightning strike, ENIAC may have run more calculations than all mankind had done up to that point.

The day is held on the 15th of February each year, in recognition of the anniversary of the first launch announcement of ENIAC in 1946. Parts of ENIAC are on public display at the Moore School, which you should visit if you're in town for PennApps. ENIAC's legacy lives on the Philadelphia area.