Question: when did the bull run battle start and end
[{'answer': 'July 21 , 1861', 'provenance': [{'wikipedia_id': '228867', 'title': 'First Battle of Bull Run', 'start_paragraph_id': 93, 'start_character': 51, 'end_paragraph_id': 93, 'end_character': 65, 'bleu_score': 1.0, 'section': 'Section::::Aftermath.:Detailed casualties.:Confederate.\n'}]}, {'provenance': [{'wikipedia_id': '228867', 'title': 'First Battle of Bull Run', 'start_paragraph_id': 1, 'start_character': 17, 'end_paragraph_id': 1, 'end_character': 679, 'bleu_score': 0.8881289058339701, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 5336983007636098041}, 'section': 'Section::::Abstract.'}]}]