PagerDuty Calendar/Holiday/Workday management and cross-regional scheduling were very poorly implemented.
The amount of manual schedule adjustment when someone actually wanted to take their 1 week vacation was insane. We ended up with overrides on top of overrides. I'd imagine some of the common tools like Workday should give you integrations for that.
Taking a holiday became like a 12 step program - email boss in advance, put in HR system request, cross check your PagerDuty schedule, negotiate a trade with another teammate for PagerDuty rotation, decline meetings, update your outlook calendar out-of-office, set your slack status & notifications, and re-remind everyone the week before you go. It's almost like they wanted it to be easier to just not take time off?
The other problem with these tools is you only get value out of them depending on the level of systems integration you spend your time on. If even a single system is not integrated & still sends emails/slacks/only updates a dashboard .. then PagerDuty is simply yet-another-tool to monitor, rather than the single pane of glass.