In Rae Hepburn's Tea Leaf Oracle, one of the three groups are the twelve months. This is to help you determine timing for some of the layouts. You can lay out the months and then the cards to see what will occur in a given month.
If you love the artwork, you can read an interview with Shawna Alexander here.
Remember that everyone who comments on this Tea Leaf Oracle series (which started on Monday of this week) will be put in a drawing. One winner will get a Tea Leaf Oracle reading done by Stella.