Question: when was the length of a year discovered
[{'answer': '2nd century BC', 'provenance': [{'wikipedia_id': '25453345', 'title': 'Tropical year', 'start_paragraph_id': 9, 'start_character': 7, 'end_paragraph_id': 9, 'end_character': 21, 'bleu_score': 1.0, 'section': 'Section::::History.:Early value, precession discovery.\n'}]}, {'provenance': [{'wikipedia_id': '25453345', 'title': 'Tropical year', 'start_paragraph_id': 9, 'start_character': 0, 'end_paragraph_id': 9, 'end_character': 392, 'bleu_score': 0.8675543090237231, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 6157338987028954917}, 'section': 'Section::::History.:Early value, precession discovery.\n'}]}]