VA Pension benefits, which includes VA Aid & Attendance, requires 90 days of active duty and at least one of those days must have been during a wartime period. Under current law, VA recognizes the following wartime periods to determine eligibility for VA Pension benefits:
Mexican Border Period (May 9, 1916 – April 5, 1917 for Veterans who served in Mexico, on its borders, or adjacent waters)
World War I (April 6, 1917 – November 11, 1918)
World War II (December 7, 1941 – December 31, 1946)
Korean conflict (June 27, 1950 – January 31, 1955)
Vietnam era (February 28, 1961 – May 7, 1975 for Veterans who served in the Republic of Vietnam during that period; otherwise August 5, 1964 – May 7, 1975)
Gulf War (August 2, 1990 – through a future date to be set by law or Presidential Proclamation)

http://www.benefits.va.gov/pension/wartimeperiod.asp