Calendar Cubes

A man has two cubes on his desk. every day he arranges both cubes so that the front faces show the current day of the month. what numbers are on the faces of the cubes to allow this?

Answer:

Note, that we must use both cubes.

Cube 1: 1 2 3 6 7 8
Cube 2: 0 1 2 3 4 5

Here the trick is to reuse 6 for 9.