This works best when it is printed two-sided and laminated. The students keep in in their math folder along with a Vis-Vis marker complete them daily during "Calendar Math" time using Expo Markers. The calendar is empty and can be filled with numbers, patterns, weather or temperature etc. Once the calendar starts filling, I may ask them to make a graph to show the weather or write a fraction to show how many days were sunny, above 70 degrees etc.
My kids love this!