CREATE TABLE table_68454 ("Date" TEXT, "Tournament" TEXT, "Surface" TEXT, "Opponent" TEXT, "Score" TEXT)

What was the date of the match against Jean-Julien Rojer, on a clay surface?
SELECT "Date" FROM table_68454 WHERE "Surface" = 'clay' AND "Opponent" = 'jean-julien rojer'
SELECT "Date" FROM "table_68454" WHERE "Opponent" = 'jean-julien rojer' AND "Surface" = 'clay'