It may help to develop a little facility with plaiting by making a much simpler model first. Use this template to make three strips of 6 squares each and braid them into a cube.
The first step in creating the calendar is to print the template on legal size paper.
Start by cutting out the pattern along the lines on the outside.
If you crease the paper where it will fold prior to cutting out the strips, your folding will be more uniform.
You'll have better results if you use a matte knife or x-acto blade to cut out the strips.
Be sure to put some heavy cardstock or a manilla folder underneath so you don't ruin your table!
As you weave your plaits together, remember that every strip goes through a simple over/under/over/under/over/under sequence. Make sure the rhombi with the calendars on them are on the outside!
A little bit of tape may help to hold the strips together as you start to weave. This isn't necessary at all, models like these hold together just fine without tape or glue. A few paper clips can also be used to hold things until the model begins to "hang together."
After you get about half-way done you may experience a certain amount of frustration: As you try to move one strip into position another tends to get pushed out. A paperclip or another scrap of tape may help preserve your sanity.
As you're finishing up, the ends of each strip need to be tucked under another strip.
Here's the finshed calendar: