global quiet time not working - still receiving alerts

Hi - 

We have 30 domain controllers that we apply OS security patches on every month.  The patches are applied at all different days of the month, but always in the evening.  When the reboot occurs, of course the domain controller is offline and therefore a slew of alerts come out.  To get around this, I found the global quiet time I could set, but it doesn't appear to be working.  We still get a ton of alerts.  I set it to occur every day from 8:30pm to 11:00pm (takes into account servers we have in various time zones).  We still receive alerts during this time.  

Any idea what I may be doing wrong?

Thanks,

Gina