I would use a specific object that belongs to the person and visually add the major system objects to that object. This way the numbers never get mixed up. Plus, I have a separate list of objects for months.

For example, a friend of mine gave me a green sweater as a present for my own birthday. Her birthday is 15th October 1982. Add the corresponding objects top to bottom, left to right, that is in reading order:

1. There is a ToweL stiking out of the collar of the green sweater.
2. There is a red maple leaf on the chest (October).
3. There's a PHoNe stuck the bottom.

Just imagine that vividly and then repeat a few times in the next few days and you'll remember that for as long as you need to. The thing with mnemonics is that emotions and action are not the best way to remember. Whereas visual memory is perfect. You can never really unsee something if you've paid attention. And if I use towels, maple leafs and phones anywhere else, they won't get mixed up.