Question: when did labor day become an official federal holiday
[{'answer': '1894', 'provenance': [{'wikipedia_id': '19156272', 'title': 'Labor Day', 'start_paragraph_id': 2, 'start_character': 428, 'end_paragraph_id': 2, 'end_character': 432, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '19156272', 'title': 'Labor Day', 'start_paragraph_id': 2, 'start_character': 0, 'end_paragraph_id': 2, 'end_character': 500, 'bleu_score': 0.9362645125346901, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 17349503243026079201}, 'section': 'Section::::Abstract.'}]}]