Question: when did bc switch from hst to gst
[{'answer': '1 April 2013', 'provenance': [{'wikipedia_id': '23921614', 'title': 'Sales taxes in British Columbia', 'start_paragraph_id': 2, 'start_character': 353, 'end_paragraph_id': 2, 'end_character': 365, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '23921614', 'title': 'Sales taxes in British Columbia', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 365, 'bleu_score': 0.968982777549629, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 15187760527396039881}, 'section': 'Section::::Abstract.'}]}]