On the unusual desk calendar shown in the
illustration a day is indicated simply by arranging the two cubes so
that their front faces give the date. The face of each cube bears a
single digit, 0 through 9, and one can arrange the cubes so that their
front faces indicate any date 01, 02, 03... to 31.
Can you determine the four digits that cannot be seen on the left
(blue) cube and the three on the right (red) cube?