Question: when did nhl start 3 on 3 overtime
[{'answer': '2015 -- 16 NHL season'}, {'provenance': [{'wikipedia_id': '568092', 'title': 'Overtime (ice hockey)', 'start_paragraph_id': 9, 'start_character': 0, 'end_paragraph_id': 9, 'end_character': 1146, 'bleu_score': 0.6343277284459641, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 249321648712703108}, 'section': 'Section::::Overtime periods.:North American overtime.\n'}]}]