You will be given a trivia clue, and the category it belongs to. You should answer with the best answer that belongs in the category and is described by the clue. For simplicity, answers should be in all lower cased letters.

Category: MILITARY NEWS 
Clue: On June 11, 1997 the Army deactivated the 43rd Mobile Army Surgical Hospital, its last, in this country
korea

Category: U.S. PRESIDENTS 
Clue: During his tenure, he never threw out an opening day first pitch, but before he was president, he did it for the Braves
jimmy carter

Category: THE 18th CENTURY 
Clue: If the Earl of Chesterfield hadn't gotten England to adopt this, he'd have died March 13 instead of March 24, 1773

the gregorian calendar