Now in its 30th year, The Mathematics Calendar demystifies math making it exciting and accessible. Each day features a different brainteaser whose solution is the date — the fun lies in figuring out how to arrive at the answer. Twelve fascinating monthly topics illustrate the role math plays in science, architecture, the arts, and everyday life. This year’s topics include Escher’s “Print Gallery,� the columns at St. Peter’s Square, satellite photography, green architecture, and stem cell research. With its creative, eye-catching design, this handsome wall calendar is as enjoyable to look at as it is to solve.