Pausing Calendar notifications during presentations
You can enable Do Not Disturb from the top of Notification Center. Open Notification Center using the button on the menu bar or swiping in from the right side of the trackpad with two fingers, then scroll up and turn the switch on.
You can also ⌥-click on the Notification Center menu bar item to quickly toggle Do Not Disturb. The icon will turn grey to indicate the change in state.