February 14 - unofficial, but widely celebrated in the professional world day programmer. February 14, 1946 the scientific world and all interested first real working electronic computer ENIAC I (Electrical Numerical Integrator And Calculator) was demonstrated.

Interestingly, the work on the development of the first computer sponsored by the American army, which the computer was needed for military calculations, planning and programming. ENIAC I worked up to 23 hours 45 minutes 2 October 1955, and then was pulled. Of course there were earlier computers, but it's all the prototypes and experimental options. If it comes to that, then the first computer in general was Babbage's analytical engine ...

But ENIAC was the first really working on practical computer tasks. Incidentally, it is from ENIACa modern computers have inherited the binary system.