Things You'll Need
Vector graphics program like Inkscape or Adobe Illustrator
Calendar reference for the year you want
Circular calendars are a visually appealing calendar style. They rely on the fact that the Earth's year is 365 days to make sure that each month takes about 30 degrees going around a circle. Drawing one yourself can be a bit challenging and is most easily done with a vector graphics computer program like Adobe Illustrator or Inkscape.
Open up your vector graphics program and set the default document size to the size you intend to print the calendar at.
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Click on the Ellipse tool, and create the largest circle you can by holding down the shift key while dragging the rim out to the edge of the paper. This will be your background circle. Write down its diameter; it will be easiest if it's in points.
Click on the Ellipse too and create a second circle that's approximately one quarter to one sixth the diameter of this one – it will be your inner bounding circle. Write down the diameter of this circle; it will be easiest if it's in points. Make sure this circle is on top of the outer circle.
Select both circles and select the Align Pallet. Make sure that the two circles are both horizontally and vertically centered with each other.
Open up a calculator, and do the following calculation: diameter of the inner circle in points, times 3.14159 (pi). This will calculate the circumference of the inner circle in points.
Divide that circumference by 84. One year is 12 months, one week is 7 days. To cover every possible permutation of days in the year, you need 1/84 of the circumference of that circle. This will be the width of one calendar box at its closest point to the inner radius.
Create a new Layer in the Layers tab. Use the polygon tool to create a shape the same width as the figure derived in the previous step. (This can be any shape you like, so long as it's no wider than 1/84 of the circumference of the inner circle.) The height should be no more than 1/10 of the difference in diameters between the two circles. Place this shape so its bottom edge is touching the outer edge of the circumference of the inner circle.
Select the shape you just made. Hit "Ctrl+M" to open the Move dialog box. Check the box that says "preview changes" and enter a vertical shift equal to the height of the shape. Hit the button that says 'copy'. A new shape will appear above the one you made. Click on that shape, hit "Ctrl+M" copy it again, offsetting it by the same amount. Repeat this step three more times, until you have five boxes aligned vertically with the bottom one touching the edge of the inner circle.
Select all five of the shapes made. Hit "Ctrl+M" to bring up the Move dialog box again. Copy the shapes with a negative vertical shift equal to the diameter of the inner circle. You should now have two rows of shapes sticking out from the top and bottom of the inner circle and just about reaching the edge of the outer circle.
Select all 10 boxes. Hit "Ctrl-G" to group them. Make sure you don't select the circles before doing this. Open up the Move dialog box. On the field that says "Rotate" and enter 360/42. Illustrator can do mathematical operations here; you want to make sure that the amount the shapes are rotated is 1/42 of a complete circle (you already have two of 84 columns of shapes in place, going in opposite directions, so you will need to do this 42 times). Click the button that says "Copy". You'll now have four radiating rows of shapes coming from the inner circle to the outer. Selecting the newest rows of boxes made, repeat the copy and rotate step 40 times to fill shapes all through the circle.
Create a new layer on the Layers palette. Copy all the shapes on the second layer to the third layer. Lock the second layer.
Use the Text tool to enter the numbers of specific days in each shape on the third layer, going in rows for each week; after you enter the last day of each week go to the next row of shapes inward to the inner circle. Delete unused shapes when you don't need them to create a day. Repeat for each month.
Use the text tool to insert the names of the month on the inner circle, rotating each month by 30 degrees in turn.
The calendar file above prints to a 22 by 17 poster sized calendar; unless you have a high-end color printer and a lot of ink to burn, it is going to be easier (and possibly cheaper) to print this at Kinko's than it is to print it at home.
If you're using Inkscape, the keyboard commands for Group, Move and Copy will be the same; for the step where you're rotating copies of the shapes for individual months, you'll need to enter 8.57142 degrees rather than 360/42.