Question: what is the line in the middle of a time zone that in theory determines the time of that zone
[{'answer': 'mean solar time', 'provenance': [{'wikipedia_id': '30890', 'title': 'Time zone', 'start_paragraph_id': 7, 'start_character': 112, 'end_paragraph_id': 7, 'end_character': 127, 'bleu_score': 1.0, 'section': 'Section::::History.:Early timekeeping.\n'}]}, {'provenance': [{'wikipedia_id': '30890', 'title': 'Time zone', 'start_paragraph_id': 55, 'start_character': 0, 'end_paragraph_id': 55, 'end_character': 381, 'bleu_score': 0.9699161750394991, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 12792598692541640116}, 'section': 'Section::::Skewing of zones.\n'}]}]