In the same way that a number can be represented by an image (and then the image imagined in a story that helps recall), a month date can be memorised by learning 366 images for the 366 days of a leap year.
I want there to be 30 hairstyles (like the 30 days in many months; the 31st would be represented by baldness on a person image); and I want there to be 12 cartoon face shapes like the 12 months of a year. In this way, the thought of a date in the year implies the outline of what a visual representation of that date looks like.
I would also want to rotate the use of cartoon features in these people's visual depiction:
trying to create variety despite there not being many ways to differentiate the cartoon people.
Within a leap year, there are 366 days. If day 1 is formatted as 001 then any of those days can be expressed as three digits. The first digit would be 0 or 1 or 2 or 3; the other digits span 0 to 9. I can use those digits to represent physical features.
0 to 3 can represent 3 types of nose. 0 to 9 can be 10 types of male hairstyle. The other 0 to 9 can be 10 types of eye.
For variety, hair colour can be a loop of colours 0 to 10 of the colours system lesson.
There is an opportunity here to associate common forenames and surnames with these 366 people; and then, imagining one of these people can imply either a date or a forename or a surname.