SEPTEMBER 2001 OR LATER , AUGUST 1990 TO AUGUST 2001 , MAY 1975 TO JULY 1990 , VIETNAM ERA (AUGUST 1964 TO APRIL 1975) , FEBRUARY 1955 TO JULY 1964 , KOREAN WAR (JULY 1950 TO JANUARY 1955) , JANUARY 1947 TO JUNE 1950 , WORLD WAR II (DECEMBER 1941 TO DECEMBER 1946) , NOVEMBER 1941 OR EARLIER , -1