It is certainly not one of the more common features that we have learned about on Mac, but Reddit user robbiegd has discovered a little trick pertaining to Notification Center on OS X Mountain Lion. If you hold down the Alt/Option key while clicking the Notification Center icon in the top right of the menu bar on Mac, it will automatically set banners and alerts to pause and resume the following day.
A toggle switch will appear in Notification Center that allows you to turn on or off alerts and banners. If you want to set Notification Center back to default settings, you must again hold down the Alt/Option key and click the menu bar icon. If you’re unfamiliar with Notification Center, it is a new feature in OS X Mountain Lion that alerts you about iMessages, Mail, FaceTime calls, Reminders and more.