Age discrimination in the US at least is driven by “40 or over”. I think any lawyer would be able to argue that “which day of the year you’re born” is not indicitive of a protected class. Because we’re fucked in the US and you can still formally be passed up on a job for being under 39 years old as long as you it’s not because “you’re almost 40, and we’re not allowed to get rid of you when you turn 40”