Let's say you want to compare two Tuesdays or look at January 14, 20 and 24 side-by-side as shown in following image. You can do that by following these steps:
- Have Calendar open (if not open, click Calendar in the left navigation pane).
- Press and hold CTRL while you select dates from the little calendar on the right-side of the screen in the To Do Bar.
As you select dates, they'll immediately appear in the main calendar screen. Select a date again to remove it from the calendar screen.