Question: when did the first episode of spongebob air
[{'answer': 'May 1 , 1999', 'provenance': [{'wikipedia_id': '14192132', 'title': 'SpongeBob SquarePants (season 1)', 'start_paragraph_id': 1, 'start_character': 164, 'end_paragraph_id': 1, 'end_character': 178, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}, {'provenance': [{'wikipedia_id': '14192132', 'title': 'SpongeBob SquarePants (season 1)', 'start_paragraph_id': 1, 'start_character': 17, 'end_paragraph_id': 1, 'end_character': 770, 'bleu_score': 0.914370438824726, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 18279322873395810149}, 'section': 'Section::::Abstract.'}]}]