You can process iPhoto calendar documents using iCalamus in all
versions iPhoto '06 and later. iCalamus usually ships with the
Photographerbook plug-in, which offers a new document service called
Photographerbook
in the default documents. The photo book print
service Photographerbook offers to print iPhoto calendars for a better
price than Apple.
Here is how it works:
Export your calendar from iPhoto in PDF format. In the iPhoto
menu, choose File > Print > PDF > Save as PDF
.
Launch iCalamus.
Create a new document using the Photographerbook
document service. Choose the iPhoto Calendar
format that you
want from the various formats available. Choose the same number of
months as you set up in your iPhoto calendar.

Now you will see an empty calendar document.
Drag the previously exported iPhoto calendar PDF into the empty iCalamus document. The PDF will automatically be distributed into all of the pages and scaled properly.
Done!
You may then proceed to format the calendar document with the iCalamus tools, add elements, or cover some content, or even use the calendar artwork without the images.
When you are ready to order the calendar document, choose the menu
item Order Document
from the File menu
.