Question: when was the last time the canadian anthem was changed
[{'answer': '2018', 'provenance': [{'wikipedia_id': '22504', 'title': 'O Canada', 'start_paragraph_id': 1, 'start_character': 701, 'end_paragraph_id': 1, 'end_character': 705, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '22504', 'title': 'O Canada', 'start_paragraph_id': 1, 'start_character': 0, 'end_paragraph_id': 1, 'end_character': 1028, 'bleu_score': 0.707800207379454, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 3644635881004604242}, 'section': 'Section::::Abstract.'}]}]