user: Question: What is Date, when Constellation is "Delphinus"?
Columns: ['HD designation', 'Constellation', 'Distance ( ly )', 'Spectral type', 'Signal power ( kW )', 'Date sent', 'Arrival date']
Types: ['text', 'text', 'real', 'text', 'real', 'text', 'text']
Sample row: ['HD197076', 'Delphinus', 68.5, 'G5V', 126.0, 'August 29, 2001', 'February 2070']
SQL:

assistant: SELECT "Date sent" FROM "Table" WHERE "Constellation" = 'Delphinus';