While moviegoers are long past the days of rushing to the movie theater to make it to their seats before the listed showtime, AMC is now giving a courtesy heads-up that’s hard to miss. Previews and various advertisements have almost always come before movies in theaters, and that aspect won't ...
Miriam is the only dictionary which included that bit, and I assume it’s because you can describe any event start as showtime.
But commercials are not the show.