The Calendar is the location in canvas where you can view all upcoming and past assignments.
In the top right corner you can change how much of your calendar you see at one time.
On the far right you can view all the classes you are enrolled in and the color that corresponds with the calendar
Below that you can click on the calendar feed and transfer the canvas calendar data to a differant virtual calendar.
In the top left you can change the month you're viewing, or snap back to the current month.
You can also create your own calendar event by clicking the "+" button on the top right and filling in the required information.