I think it has an effect, not inherently, but only because we then standardize schooling based on birth year, not actual age. Starting at four years and one month vs four years and eleven months (where I am, it starts even earlier, at two years and six months/three years and five months for kindergarten) means students are in a wildly different developmental stages. I don’t think it’s necessarily a lifelong thing, but at least during school, the kids who start at a later age are better at sports, so they’re more likely to make sports teams, which certainly affects your personality.

I would never say that I believe in astrology though.