Article details how to view multiple calendars at the same time.
Each calendar you check opens next to calendars that were already showing. This is the side-by-side view.
Tip You can drag calendar items from one calendar to another to make a copy, as long as you have the required permission.
You can combine all of the open calendars into a single calendar view.
Each calendar is transparently stacked on top of one another. In this combined calendar view -- overlay view -- it's easy to identify free/busy times among multiple calendars. When you see an empty time slot, you know there's nothing scheduled on any of the calendars in the overlay view.
That calendar is overlaid with the one you opened first -- usually your default calendar. Repeat for each calendar you want to add.
When you no longer want to view a calendar, uncheck it in the Folder Pane, or on the calendar tab, click Close Calendar