Question: when did the battle of antietam take place
[{'answer': 'September 17 , 1862', 'provenance': [{'wikipedia_id': '84849', 'title': 'Battle of Antietam', 'start_paragraph_id': 105, 'start_character': 1367, 'end_paragraph_id': 105, 'end_character': 1386, 'bleu_score': 1.0, 'section': 'Section::::Aftermath.\n'}]}, {'provenance': [{'wikipedia_id': '84849', 'title': 'Battle of Antietam', 'start_paragraph_id': 1, 'start_character': 23, 'end_paragraph_id': 1, 'end_character': 508, 'bleu_score': 0.605185086511815, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 7002311419310617907}, 'section': 'Section::::Abstract.'}]}]