Question: when does the 2018 nfl free agency start
[{'answer': 'March 14', 'provenance': [{'wikipedia_id': '48479614', 'title': '2018 NFL season', 'start_paragraph_id': 3, 'start_character': 53, 'end_paragraph_id': 3, 'end_character': 61, 'bleu_score': 1.0, 'section': 'Section::::Player movement.\n'}]}, {'provenance': [{'wikipedia_id': '48479614', 'title': '2018 NFL season', 'start_paragraph_id': 3, 'start_character': 0, 'end_paragraph_id': 3, 'end_character': 781, 'bleu_score': 0.8016563566637671, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 15236756993296839636}, 'section': 'Section::::Player movement.\n'}]}]