Question: when did the british north america act take effect
[{'answer': 'July 1 , 1867', 'provenance': [{'wikipedia_id': '37750', 'title': 'British North America Acts', 'start_paragraph_id': 3, 'start_character': 104, 'end_paragraph_id': 3, 'end_character': 117, 'bleu_score': 1.0, 'section': 'Section::::Constitutional change.\n'}]}, {'provenance': [{'wikipedia_id': '37750', 'title': 'British North America Acts', 'start_paragraph_id': 3, 'start_character': 0, 'end_paragraph_id': 3, 'end_character': 931, 'bleu_score': 0.986969988197764, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 16556381390843985363}, 'section': 'Section::::Constitutional change.\n'}]}]