In order to complement the round shape of the calendar, I created my own numbers with perfect round shapes. There is also a symbol for each month. For instance, April has a raining symbol and March has clover leaf.
I think doors are the most frequently used object in a house. It is also a good place to remind yourself of up coming events. One side of each month has all the dates and the other side provides you a lot of space to write on. You can also write phrases to remind your roommate you are busy or asleep.