CREATE TABLE table_50596 ("Outcome" TEXT, "Date" TEXT, "Tournament" TEXT, "Surface" TEXT, "Opponent in the final" TEXT, "Score in the final" TEXT)

What is Date, when Outcome is 'Winner', and when Surface is 'Grass'?
SELECT "Date" FROM table_50596 WHERE "Outcome" = 'winner' AND "Surface" = 'grass'
SELECT "Date" FROM "table_50596" WHERE "Outcome" = 'winner' AND "Surface" = 'grass'