Yes, same day change will allow you provided the same fare class is avalaible to take a flight as much as 24 hours prior to your scheduled departure, paying only a change fee, only $25.00 if you are Gold status.
I thought the rule allowed standby for a flight if the same fare class was not avaliable. I found out the hard way standby for a flight is only allowed the same DAY. This can be confusing since SDC allows changes when it is not the same DAY.