user: Question: What is the Date of the match against Guillermo Olaso?
Columns: ['Outcome', 'Date', 'Category', 'Tournament', 'Surface', 'Opponent', 'Score']
Types: ['text', 'text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Winner', '21 July 2008', 'Futures', 'Irun, Spain', 'Clay', 'Pablo Martin-Adalia', '7–6 (7–1) , 7–6 (7–4)']
SQL:

assistant: SELECT "Date" FROM "Table" WHERE "Opponent" = 'Guillermo Olaso';