CREATE TABLE table_68458 ("Outcome" TEXT, "Date" TEXT, "Surface" TEXT, "Opponent" TEXT, "Score" TEXT)

What date was the surface hard and Eva Hrdinov was the opponent?
SELECT "Date" FROM table_68458 WHERE "Surface" = 'hard' AND "Opponent" = 'eva hrdinová'
SELECT "Date" FROM "table_68458" WHERE "Opponent" = 'eva hrdinová' AND "Surface" = 'hard'