CREATE TABLE table_3499 ("Institution" TEXT, "Location" TEXT, "Founded" FLOAT, "Type" TEXT, "Enrollment" TEXT, "Nickname" TEXT, "Joined" TEXT, "Left" TEXT, "Football Conference" TEXT, "Primary Conference" TEXT)

What date did the institution that left in 2013 and that is nicknamed Corsairs, join?
SELECT "Joined" FROM table_3499 WHERE "Left" = '2013' AND "Nickname" = 'Corsairs'
SELECT "Joined" FROM "table_3499" WHERE "Left" = '2013' AND "Nickname" = 'Corsairs'