TO CELEBRATE its fiftieth anniversary, the National Archives has planned a special exhibition, “Recent America,” which opened June 19 and will run through Labor Day, 1985. Hours are 10:00 A.M. to 9:00 P.M. daily through Labor Day, and 10:00 A.M. to 5:30 P.M. during the winter months. Movies and lectures will be offered as part of a “kaleidoscopic look” at the period, according to the archivist, Robert M. Warner.