We're in Eastern Time and tend to travel west more often than not, so time zone changes mean our kids end up in bed later by default. A 7 PM bedtime here means we'd be starting our bedtime routine in the middle of dinner in Central or Mountain time!
We do try as much as possible to stick to the same times. However, time changes are another story. Last year we went to Maui and our 5 year old woke up, put her bathing suit on and wanted to go to the pool at 2 a.m. since we put her to bed at her normal bedtime at home. So, we have learned to be a bit more flexible with bedtimes on vacations.