The Calendar Math sheet covers multiple common core math standards including 2.NBT.3, 2.NBT.1, 2.OA.3, 2.NBT.8, 2.MD.8, and 2.NBT.2. The students become very fluent with these standards by the end of the year due to the daily repetition of each of the standards.
I use the Calendar Math sheet as bell work each morning. I copy this sheet into a book that last the entire school year for each student so it is readily available for them each day. The school day number is posted on the board each day and the students answer the calendar math questions using the school day number. We go over the answers after my "secretarial duties" are done each morning.