A calendar typically has 12 months… and what shape has 12 sides? A Rhombic Dodecahedron. And they are quite easy to make.
The hardest thing is printing all the months in exactly the right places. Here is a template for the 2020 Rhombic Dodecahedron Calendar based on 6 different coloured sheets of A4 office paper. Chop each into 2 sheets of A5, and you’ll have the material you need.
Template for the Rhombic Dodecahedron Calendar 2020 – A4 Format (PDF)
(Instructions yet to come.)
Next step is Origami Flowers.