April 21st (1964) was a Tuesday. It's the 110th day of the year (111th in leap years) in the Gregorian calendar. There are 255 days left to the end of the year.
Historical Events for 21st April, 1964
» A Transit (satellite) Transit-5bn satellite fails to reach orbit after launch; as it re-enters the atmosphere, convert 2.1 lb of radioactive plutonium in its Systems Nuclear Auxiliary Power Program SNAP Radioisotope thermoelectric generator RTG power sour