I don't know about the time of meal change, but I wanted to tell you don't plan on being seated at your ADR time.
We wet to 50sPT in November. We arrived about 15-20 minutes before our ADR time and waited over an hour past our ADR time to be seated. We were there over 3 hours and that included taking dessert to go. We have been before and while this was by far the worst for time, we have never gotten in without a good wait (far past any other ADR wait). Just to let you know. We love it there but this time the wait was just too much. I hope you have better luck then us, but I would not plan on being seated till after 4pm.
Good Luck!!!