Question: when did labor day became a 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': 15, 'start_character': 0, 'end_paragraph_id': 15, 'end_character': 722, 'bleu_score': 0.9826823455989031, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 1954423164380988785}, 'section': 'Section::::Labor Day vs. May Day.\n'}]}]