These calendar numbers feature the diamond shape! Another teacher requested them and I thought it was a great idea! You can teach shapes to the kids while tracking the date! Purchase some or all of the other sets (square, triangle, etc.) and teach patterns to your students as you go!
The set features a larger card to be used when introducing the shape to the class. It's great because it contains a larger version of the SAME shape they will see on the calendar (same color, font, etc.) and includes a description/definition of the shape.
These cards could also be used in a math center. Kids can place cards in number order but they can also challenge themselves by creating their own pattern when this set is purchased with another shape.
Just print the pdf and trim. For extra protection from frequent use, you can laminate!