it's seen as medieval, say 300 years earlier than it was written; but this doesn't really mean anything. Some of Shakespeare's historical plays (Julius Caesar, eg) are obviously set in earlier eras, while others were seen as being 'in the present time', but they would all have looked contemporary. The actors would generally have worn Elizabethan dress (they might just have dug out a toga for a Roman play) and the lines are all in Elizabethan English with no attempt at historical accuracy, which is a purely modern concern.