If you’re the kind of person who reads a blog about math worksheet then perhaps you’ll think that this is interesting: a clock that uses only the number nine to represent the digits 1 through 12.
You may note that some of the entries aren’t consistent with the ideal that the simplest solution is the most elegant. The entry for 9, for example, could have simply been “9”.
I think the ideal for this clock is for every hour to be expressed using three 9’s — so the number 1 should be represented by 9 **(9-9) — nine to the 0th power. Fun clock!