If you are going to see Rod at a festival (like Glastonbury or something similar), throw all the rules out the window. Festival time is a suggestion, not a promise. He could be on at 6:00 PM because it’s still light out, or he could be the headliner at 10:00 PM because the organizers want everyone to be properly tipsy.
My advice? Find the festival map. Walk to the main stage. Look at the crowd. If you see a sea of people holding lighters (or phone flashlights) and wearing leopard print, you are in the right place. That means Rod is imminent.
Also, if you’re in Las Vegas for a residency, the start time is basically a contract. They don’t mess with Vegas start times. The casino wants you to lose money after the show, so Rod will be on at 8:00 PM sharp and off by 10:15 PM. He’s efficient. He’s a professional. He’s also probably hitting the poker table afterward.