Use the following shortcuts to get the most out of your calendar...
Undo changes you've made to events: click the "undo" button at the bottom of the screen before it fades away, or use the keyboard shortcut Shift-Z at any time to undo your last edit.
Double-click any blank space in the calendar to begin creating a new event.
Or drag the plus button from the lower right to any cell in order to start a new event.
Double-clicking on the clear space on any day also brings up an option to jump to that day on the Day tab.
Click on the little arrow to the left of the date to hide the calendar's sidebar and make more room for the calendar itself.
Hold down option/control while dragging an event to duplicate it.
Hold down the shift key to select several events and drag them all at once.
Click on the date in the desktop or mobile calendar to bring up a date-picker and quickly jump to another date.
Oh horizon view, shift-clicking on the arrows on either side of "today" will move the calendar one day in either direction instead of one-page in either direction.
To add the ability to select all events on your screen using a Shift-A, or similar keyboard shortcut, you can install and customize the Select All Events custom app actions.
Change an item's status or mark your tasks done with a single click when holding down a special key. Include sounds or animations to reward you for marking things done: One Click Done.
Drag to select multiple events at once and then reschedule them. (Details and video)
Browse a list of unscheduled items and drag them into the calendar when you find an open resource. (Details and video)