I have a watch that uses MM/DD for date, which pissed me off to no end. While looking for a way to change it to DD/MM, I found out that they actually used ISO-8601 and dropped the year. Now I don't know how to feel about it.
ISO 8601 has spec for how to drop the year. You write it like --MM-DD (two dashes to indicate omission). Of course nobody really uses it beside the absolute nerds (e.g. me).