You could try and do calendar calculation…
Not sure I’ve you’ll have time to set up seven memory palaces for the 100 year codes, but you should be able to memorize the 12 month codes by then to be able to do the current year.
You could use that to show them mnemonics like “may-o-nnaise” for May = 0, etc. for the month codes or even the approach to year code memorization that I describe in the post above.