With the Periodic Calendar you get… a perpetual calendar capable of exploring dates going back to 1582 and going forward into the future as far as you want to go. a new way to look at time as the shift from day of the month to day of the week changes our… The Periodic Calendar 16″ x 38″ print of the last calendar you’ll ever need. $24.99 Free Shipping within the U.S. +$5 to Canada+$10 for Int’l Orders