I decided to make these calendars as holiday gifts for my friends and family as I thought the idea was really cool (and you'd potentially only need two calendars for the rest of your life.)  They're based on the Julian date calendar- so every day of every month is represented in a vertical strip, intersected by transparency rainbow colored boxes. (You can find out more about Julian days here if you're curious.)

 

The images are also scaleable to many different frame sizes.