Question: when did the first earth day take place
[{'answer': '1970', 'provenance': [{'wikipedia_id': '158548', 'title': 'Earth Day', 'start_paragraph_id': 1, 'start_character': 142, 'end_paragraph_id': 1, 'end_character': 146, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]