In my setup I have a number of alerts of a number of diff devices. In these alerts I have 3 times specified for the alerts to trigger. 7-5 mon-fri 5-7 mon-fri and 12-12 Sat and sun. This way I have coverage to the appropriate people duing the appropriate hours. What this does not cover is stat holidays.
What will happen is let's say Friday is the day off and a critical device goes down at 2pm. According to the setup I have built someone on the Business hours mailing list would be notified. This will not do as they'll out of the office.
So remedy this I am having to create a new custom true/false property and then create a new alert for every exisiting alert I have now. The new alert, in the trigger condition states if x is down and it's part of x group and Stat is equal to true then alert. I then have to go into every existing alert and create a suppresion for it not to fire if Stat is true.
Now when a stat holiday comes up (Next week) I will have to manually change the custom property from False to True.
I would like to see a feature that would make this process easier as I don't believe that I am alone in this setup.
It's not currently possible to easily exclude specific days for alerts (as you have discovered). I will log this as a feature request. Thanks for the feedback.