Subscription status incorrect. Old plus new?

I seem to recall that if I renewed my subscription that the existing time left with the current subscription would be added to the new subscription.  That is, if I had 14 days left and renewed, the new subscription time would be 14 days (old) plus 366 days (new), that is, 380 days left.  This did not happen.  Both versions are the same, Norton 360.  Did I make the wrong assumption and the subscription period starts when the product is activated?   Can I reload at the end of 14 days and get the subscription status back to 366 days remaining?