user: Question: What is the date for the Grass surface final against Nathan Healey?
Columns: ['Date', 'Tournament', 'Surface', 'Opponent in the final', 'Score']
Types: ['text', 'text', 'text', 'text', 'text']
Sample row: ['2 October 2007', 'Sawtell , F6', 'Clay', 'Miles Armstrong', '6–1, 6–3']
SQL:

assistant: SELECT "Date" FROM "Table" WHERE "Surface" = 'Grass' AND "Opponent in the final" = 'Nathan Healey';