How do I return to the old calendar, please?

How do I return to the old calendar, please?

I clicked on "Try the new calendar" this morning, actually I had no choice because the "Try" message hid most of my calendar.

I do not like it one bit. In my opinion it looks terrible compared with what it used to be.

So how do I return to the old calendar?

A quick answer is appreciated, before I find another calendar to use.