Question: when did the battle of khandaq take place
[{'answer': 'January / February AD 627'}, {'provenance': [{'wikipedia_id': '1168834', 'title': 'Battle of the Trench', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 332, 'bleu_score': 0.5484500966242131, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6463356370362826729}, 'section': 'Section::::Abstract.'}]}]