A calendar with a difference not only does this calendar boast a unique geometric design, but it also has heat-sensitive ink on each day hiding a fascinating fact. Simply choose your date, touch the black square and watch it disappear to magically show a fact about that specific day in history. The blank ink only disappears temporarily so once the square has cooled, the fact is then hidden again. Plus, the unique design provides space for you to write down all your daily tasks too.