I always thought the dodecahedron would make a perfect calendar.
Now updated for 2013.

Step 1: Required Tools

To make the calendar you will need a scissors, X-acto knife or similar, tweezers, and a toothpick.

Step 2: Download Template

Download the template PDF from the link below the image preview box. Print and cut out the twelve months. Plain paper will work fine but a heavier, bonded paper will stay flat better.

To draw your own pentagons:
The pentagons I used are 2 inches on a side and there are three different rectangles for the months. Months have 4, 5, or 6 rows plus one for the month name.
For the 7x7 square the side length is 2.12" and the center is 1.83" up from the bottom point of the pentagon.
For the 7x6 rectangle the size is 2.2" across, 1.9" vertical, and the center is 1.77" up from the bottom point.
And the 7x5 rectangle is 2.35" across, 1.68" vertical, and the center is 1.69" up from the bottom point.

These measurements will get the rectangle centered in the pentagon with the corners reaching the sides. To make a larger or smaller calendar I'd recommend dividing these measurements by 2 and multiplying that by the length of the side of your pentagon.

The tabs measure about 1/2 inch in from each corner and are 1/3 inch wide. The lines in the tab divide the tab in 3.

I had to use a CAD program, but more talented people could likely draw this out.
See my other instructable, Drawing a Pentagon.

Step 3: First Fold

Fold the trapezoid shapes back using the edge of a table or a metal ruler.

Step 4: Tabs and Slots

Each trapezoid shape can be either a tab or a slot depending on which you need.

Step 5: Cutting Slots and Tabs

To make the slot, cut line B between lines C with the X-acto knife.  To make a tab, cut both lines A and then fold the wings back behind to make a squarish tab.  Check the second image in this step for a hint on cutting the tabs.

Step 6: Begin Assembly

When I assemble the calendar I make slots in the pentagon sides that I'm not yet connecting to another pentagon and put tabs in the pentagon sides that I'm about to attach to the assembly. So on the first pentagon I put slots on all five sides. On the second pentagon I make one tab and four slots. On the next three pentagons I make two tabs and three slots. And for the last pentagon I cut tabs on all five sides. Don't get ahead of yourself on the tabs and slots. Cut out the tabs and slots on each pentagon as you need them just prior to assembling it onto the dodecahedron.
Don't get too hung up on what "I" do this and "I" do that.  If you can imagine a better way to keep the tabs and slots straight, go for it.

Step 7: Unfolding the Tabs

Insert each folded tab into a slot such that the trapeziod shapes are on the inside of the dodecahedron.  After putting each tab into the slot, unfold the tab so the connection is permanent.

Step 8: Partially Complete View

Keep adding pentagons around the edge of the first pentagon.  Remember to cut out slots and tabs on ALL FIVE edges of each pentagon as you are about to attach it to the assembly.  Cutting out tabs and slots on a pentagon already assembled onto the dodecahedron is nearly impossible.  Use the tweezers to insert the folded tabs into the slots as you run out of room for your fingers.

Step 9: Unfolding Final Tabs

On the last pentagon the tweezers will be a must.  You will also need to use a toothpick to reach inside the dodecahedron to unfold the tabs.  Unfolding the last tab may be optional as the dodecahedron should hold itself together by now.
<p>I had an idea for a rotating calender, on an axis, with of course 12 faces, it would be more convenient than page flipping- back and forth. So I looked online but couldn't find one anywhere. The dodecahedron looks great, I would prefer to purchase one rather than struggle, but I can see that once a person has mastered it, it would be fun to make. Just to hark back to my pursuit of the rotating calendar, It would be even better with insertable cards[ for each month] so that they could be replaced each year.</p>
I like the idea of a dodecahedron calendar but fitting it all together gets awkward on the last couple of sides. So I've made an adaption which makes it far easier to put together. Accepting the fact that the calendar will need to move around a lot, I have made it in two halves that slot together. One half has tabs and the other half has slots. It's then very easy to stick the side together in each half and slotting them together requires no glue at all. In fact I prefer using double sided adhesive tape. I like the shape to be quite solid so I use 400gsm thick card which works very well. Although this is too stiff to go through the printer, adding the calendar months can be achieved by printing them on self-adhesive paper (I use white vinyl), then cutting them out in pentagon shape and sticking them on each month side. If anyone is interested I can send the template file in whatever format is desired.
<p>Have you tried combining this idea with the tab/slots that I use. They are quite permanent and not at all as messy as glue. Also, how large is the final dodecahedron. Putting it all on one sheet must limit the size.</p>
<p>Actually, since I sent the calendar out instead of a Christmas <br>card, my criteria was that it had to be assembled easily. It was <br>sent flat through the post with all the fold lines perforated and <br>double-sided adhesive already fixed to the tabs &ndash; with the top <br>release paper left in position. One recipient was disabled and <br>another was elderly, so assembly had to be easy. I sent it along <br>with some pictorial DIY instructions. I scaled it to the largest <br>size that would fit on an A3 sheet of cardstock &ndash; one half to each <br>full sheet &ndash; and when assembled it measures around 5.5 inches at <br>its widest points and 4.5 inches from top to bottom. This is still <br>large enough to read all the numbers and still enabled me to add <br>minimal graphics (<a href="http://www.paulsroom.co.uk/139616226" rel="nofollow">http://www.paulsroom.co.uk/139616226</a>). <br> I appreciate that with your tabs the shape has no protrusions like <br>mine; but I designed the tabs so that once each half was folded and <br>stuck along the long tabs, it just slotted together. It's a closed <br>shape because the tabs make it self-locking and if you drop it, it <br>will not come apart.</p>
Sorry, this should have said NOT move around. Although even with the unglued slotted state, it's still quite solid.
I've just finished making this, it took about 2 hours. It was relatively easy, putting the last piece on was pretty hard and it's kind of fragile. It turned out great though (:
Has anyone made this, or are the instructions too hard to follow?
can you just make it a perpetual one? i mean that can be used for many years???<br /> <br />
I've made a dodecahedron out of 1/2 inch thick foam pieces.&nbsp; Looks pretty good but then you'd be stuck &quot;sticking&quot; months on each side cut from paper every year.&nbsp; Some of the spray-on adhesives are temporary, but it would be an un-godly mess.&nbsp; You'd be spraying it, picking it up, then unsticking your fingers to set it down in the overspray.&nbsp; Then picking up the next month with sticky fingers.<br /> <br /> Making something permanent would be even more difficult.&nbsp; Perhaps writing out the months with day one in the upper left corner in each month.&nbsp; Then you would need some temporary way of marking which column is Sunday.
Cool, that would look great on my desk.<br />
There are alternative additional approaches and templates for similar calendars: <br /> &nbsp;&nbsp;&nbsp;&nbsp; - dodecahedron calendar template that is cut out in one piece as opposed to 12 separate pieces<br /> &nbsp;&nbsp;&nbsp;&nbsp; - completely origami version that doesn't require tape or cutting<br /> &nbsp;&nbsp;&nbsp;&nbsp; - rhombic dodecahedron version that doesn't require tape or cutting<br /> &nbsp;&nbsp;&nbsp;&nbsp; - a flat star calendar assembled from 12 separate folded pieces<br /> <br /> The 2010 version of each of these is available from the following link: <a href="http://www.origami-resource-center.com/origami-calendars.html" rel="nofollow">www.origami-resource-center.com/origami-calendars.html</a><br /> <br />
I did visit the site you listed.&nbsp; I like the rhombic version but this one will sit on my desk.&nbsp; Personally, I like this one because I designed it.&nbsp; I didn't have to go somewhere to be instructed how to build it.&nbsp; <br /> I plan on updating the site by November for 2011.

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