Toggle Notification Center's Do Not Disturb on OS X Yosemite. Brought to you by Automator.

notification center.scpt

-- Toggle Notification Center's DND on Yosemite
tell application "System Events"
	option key down
	delay 0.1
	
	try
		click menu bar item "Notification Center" of menu bar 2 of application process "SystemUIServer"
	end try
	try
		click menu bar item "NotificationCenter, Do Not Disturb enabled" of menu bar 2 of application process "SystemUIServer"
	end try
	
	option key up
end tell

Another variation to get El Capitan to work.....
from ... http://applehelpwriter.com/2014/12/10/applescript-toggle-notification-centre-yosemite/comment-page-1/

tell application "System Events"
    tell application process "SystemUIServer"
        try
            if exists menu bar item "Notification Center, Do Not Disturb enabled" of menu bar 2 of application process "SystemUIServer" of application "System Events" then
                key down option
                click menu bar item "Notification Center, Do Not Disturb enabled" of menu bar 2
                key up option
            else
                key down option
                click menu bar item "Notification Center" of menu bar 2
                key up option
            end if
        on error
            key up option
        end try
    end tell
end tell