CREATE TABLE table_38731 ("Date" CLOB, "Tournament" CLOB, "Surface" CLOB, "Opponent in the final" CLOB, "Score" CLOB)

What date is the z rich, switzerland tournament?
SELECT "Date" FROM table_38731 WHERE "Tournament" = 'zürich, switzerland'
SELECT "Date" FROM "table_38731" WHERE "Tournament" = 'zürich, switzerland'