CREATE TABLE table_70084 ("Date of Issue" TEXT, "Theme" TEXT, "Denomination" TEXT, "Printer" TEXT, "Quantity" TEXT, "Design" TEXT, "Perforation" TEXT, "First Day Cover Cancellation" TEXT)

When did the Theme of bobsleigh release?
SELECT "Date of Issue" FROM table_70084 WHERE "Theme" = 'bobsleigh'
SELECT "Date of Issue" FROM "table_70084" WHERE "Theme" = 'bobsleigh'