November 13, 2015, when expressed in MM/DD/YY format, is 11/13/15. The MM, DD and YY terms, in that order, form an arithmetic progression. It is non-trivial because the three numbers are different.
The first such date in any given century is 01/02/03. What is the last non-trivial arithmetic progression in the century?
What is the last non-trivial geometric progression in the century?