There are a few methods you can use to print out your Owl Calendar, but printing directly from your web browser will likely cause formatting issues. The method you decide to use will depend on how you want the printout of your Owl Calendar to look.
One method would be to first export your Calendar as a CSV or PDF file. You can do this by using the Export button in the top left of the Calendar. Doing this would enable you to print off this file with no issues, although these exports would not resemble the layout of the Owl Calendar in your browser.
The best way to print out a physical copy of your Owl Calendar that resembles how it looks in your browser would be to do a quick screen capture, and then print out that screen capture.
On a Mac, the easiest way to do this is with the following keystroke: Command + Shift + 4.
On a Windows, you need only press the Print Screen button on your keyboard.