Question: when was the last time a veto was overridden
[{'answer': 'September 23 , 2016'}, {'provenance': [{'wikipedia_id': '1390880', 'title': 'List of United States presidential vetoes', 'start_paragraph_id': 434, 'start_character': 0, 'end_paragraph_id': 434, 'end_character': 227, 'bleu_score': 0.5498929873828431, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 15556853815363336070}, 'section': 'Section::::Vetoes cast.:Barack Obama.\n'}]}]