CALENDAR SOLVED • • • • •   Because there are ten digits but only six faces per cube, we know that some of the ten digits will appear only on cube A and others will appear only on cube B. However, we have to be able to precede any of the digits with 0 (for dates 01 through 09), or with 1 (for dates 10 through 19), or with 2 (for dates 20 through 29). Therefore whichever cube a digit is on, the other cube must contain the digits 0, 1, and 2.  That means that 0, 1, and 2 must appear on both cubes. (To display 30 and 31, the 3 that appears on only one cube can be paired with the 0 or the 1 from the other cube.) So each cube has 0 1 2.  Three faces remain unassigned on each cube, for a total of six faces.  Onto those six faces we have to fit the remaining seven digits, 3 4 5 6 7 8 9. How can we fit seven digits onto six faces?  Put 3 4 5 on one cube and 6 7 8 on the other.  When a 9 is required, just turn the 6 upside down. Cube A Cube B 0 0 1 1 2 2 6 3 7 4 8 5

UPDATE, SEPTEMBER 19, 2010:  I was listening to NPR's Car Talk yesterday morning and heard Click and Clack describe their new "puzzler" for the week of 09-20.  It was the same as a question I posed here in 2007.  Those pirates! UPDATE, JANUARY 10, 2017:  The lower right corner of my computer screen keeps me apprised of the date, but not the day of the week.  So I fixed up my own little wooden block (right) to fit into a notch in my desk. Click here to return to my Archive.