It 's the funniest calendar of the year! says Gene Shalit. Habit-forming, proclaims "Maxim." It 's also one of our top-selling calendars, a charming and lighthearted paean to play and spontaneous fun. Every month, "Nuns Having Fun" peeks behind the veil of convent life, offering an unexpectedly delightful image of nuns on their downtime kicking back, letting loose, having a great time with their sisters. Nuns on water-slides. Nuns square-dancing. Nuns in the dugout and nuns on ice. The black-and-white retro photographs are warm and lively, and pay fitting tribute to the nuns of yesterday and today. Witty commentary is provided by Maureen Kelly and Jeffrey Stone, co-authors of the "New York Times" bestseller "Growing Up Catholic."