You can show up late. I am not sure if it is long as one hour after assigned time. They will let you in 5 minutes prior to assigned time and sometimes sooner depending on volume.
If I knew we were running late and in jeopardy of missing our assigned time, I would go into the booking and modify it for a later time (usually an hour later). I did that several times for the same booking and pushed it as far out as 2 hrs past the original time.