Unsolicited Advice: Clearly communicate your show times
Venues and concert promoters should provide clearly available intel for those who disregard the above and just want to see the headlining band. It's not a lot of work! There's only two steps.
While we are very pro "see the opening band," we know not everyone wants to do that.
The CIA... An angry spouses' internal monologue. The actual show times of a concert you're hoping to see. There are some things that are deemed national security issues.
While every venue is different, every experienced concertgoer has had the frustrating experience of any one of the following:
1) Trying to find the actual show page that ostensibly lists the acts and the order in which they go on.
2) Doing the mental math of when the doors will open, when the first band will ostensibly be going on, and so forth, to pick the appropriate time to show up to ensure you don't miss the act you want to see.
3) Showing up on time, only to find the previous act took forever to start and now you're still waiting.
Again - we get it - concertgoers should show up early and experience the openers - especially if they don't know them. You buy tickets for the whole experience, and, if you like Band X, you're bound to enjoy the up-and-coming bands they chose to open for them. Or, for festivals, trust in the curators' vision for who should lead up to the band everyone is there to see.
But, nonetheless, venues and concert promoters should provide clearly available intel for those who disregard the above and just want to see the headlining band. It's not a lot of work! There's only two steps.
1) Clearly promote the day's show on your home page, with clear estimated start times for each band.
2) Use social media to update fans on delays and revised start times.
That's it.