It says this mare is 4 years old, but her birth year is 193. Also lists her birthday as August 21, 2025. She has already been bred once.

Same for this mare.

I have several like this.

Did you capture them as a 3 year old and not a 2 year old?

I did capture her as a 3-year-old.

That'd be why. If you capture them, their 'birthday' is just when they were created, not when they'd've hypothetically been born for their birth year and age to line up