Sixteen Candles jumps around more than a kangaroo on a trampoline. John Hughes narrative style here intends to tell jokes more than it wants to tell a coherent story. As a result, the perspective jumps around from Sam, to the Geek, to Jake, to Caroline, to even Long Duk Dong every few minutes.
Only at the school dance are all the characters in the same place. Even then, that scene is only a few minutes long. After Sam retreats to the auto shop, our character all over the place again. We don't even see her friend Randy after the dance. Did she make it home okay? Should someone check on her?
What keeps the plot from getting too confusing is that everything is told in a linear fashion. And the plot isn't that complicated to begin with. Family forgets girl's birthday. Girl agonizes over boy. Girl gets boy. The end.