Here is an interesting twist on the traditional annual calendar:
Image credit: https://bigthink.com/starts-with-a-bang/one-page-calendar/
Yes, it is a lot more efficient when it comes to the amount of space it takes (or the required font size to fit a whole year on a page). But I think the point of the big, dense, calendar is to schedule and plan things across the year. Also, you need to do a few mental steps to get your head around looking at a specific month.
I added a template with this calendar to the SlideMagic template library, search for “calendar” in the SlideMagic app and it will show up.
You can read the full discussion of this alternative calendar format here.