user: Question: What are the dates where the opponent was Guillermo García-López Albert Portas?
Columns: ['Outcome', 'Date', 'Surface', 'Partner', 'Opponents', 'Score']
Types: ['text', 'text', 'text', 'text', 'text', 'text']
Sample row: ['Runner-up', '28 April 1997', 'Clay', 'Petr Luxa', 'Mahesh Bhupathi Leander Paes', '1–6, 1–6']
SQL:

assistant: SELECT "Date" FROM "Table" WHERE "Opponents" = 'Guillermo García-López Albert Portas';