DIY Calendar – 3D Version

As a small do-it-yourself project, I wanted to make a three-dimensional calendar to sit on my desk. I decided to try a polyhedron design because that would be reasonably quick to make from cardboard.

As there are twelve months in the year, the obvious choice for the polyhedron is the regular dodecahedron with one month on each of the pentagonal faces.

But this has been done often enough that it’s looking ordinary, so I thought it might perk things up a little with another shape. One option is a 14-sided polyhedron with two hexagonal polar faces and twelve trapezoid faces for the months.

This shape should make for a good advertising give-away: the polar faces could carry a corporate logo, and the polyhedron can be contrived in such a way that it folds flat for mailing. Advertisers ought to like calendars because, if they can persuade the customer to use the calendar, the advertiser’s logo stays in the customer’s sight for a year.

However, I decided to go with another 12-sided polyhedron, the rhombic dodecahedron:

I chose it because it has a pleasing symmetry – all the faces of the polyhedron are identical, and the faces themselves are one step away from full symmetry – and those faces are four-sided which seems to suit the rectangularity of a calendar month grid.

Making Faces

The first step for this DIY calendar is to create the faces. There are templates out there that you can use, but it’s not difficult to make your own. I decided to make the face images in PowerPoint.

Lay out the rhombuses with dimensions in the ratios shown here. For accurate dimensions in PowerPoint, the Format Shape> Size dialog pane is your friend. In my case I scaled the rhombic face to be 12cm wide by 16.96cm high (4.72” by 6.68”), with each side of the face being 12.72cm (5.01”) long.

The upside of painting the month faces this way is that you can format them however you like. In my case, I adjusted the colours of the months to match the seasons – icy blue for winter, garden green for spring, sunny yellow for summer, and harvest red for fall.