Question: when did joshua tree became a national park
[{'answer': 'October 31 , 1994', 'provenance': [{'wikipedia_id': '18952869', 'title': 'Joshua Tree National Park', 'start_paragraph_id': 10, 'start_character': 389, 'end_paragraph_id': 10, 'end_character': 406, 'bleu_score': 1.0, 'section': 'Section::::History.:Protection.\n'}]}, {'provenance': [{'wikipedia_id': '18952869', 'title': 'Joshua Tree National Park', 'start_paragraph_id': 10, 'start_character': 0, 'end_paragraph_id': 10, 'end_character': 473, 'bleu_score': 0.7373124022088691, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 15981254105717117405}, 'section': 'Section::::History.:Protection.\n'}]}]