I think that the season a baby is born in does indeed affect their emotional and mental outlook from the beginning, and I’ve read at least two studies that suggest that there are health variations and longevity issues that correspond to birth season, probably having to do with temperature, food supply, light, maternal stress level during gestation, etc. I suspect that astrology is merely a pre-scientific way to try and explain these patterns.
I assume you mean the time of year on earth, totally unrelated to astrological charts (the stars). Could be, I’ve never researched it.
It might be.
This would be an area for psychologists to delve into. Being good secular scientists and not accepting the supernatural as part of their world view, they would call the correlations a coincidence. Whether spiritually minded people would take this further would be up to them.
The model you suggest — gross seasonal effects — might explain why the imputed birth sign of a person has not changed with the procession of the equinoxes. Horoscopes “cast” that way would “work better.”
They’d need to consider people in the Southern hemisphere, too. The seasons are reversed there.
So people born in October here are Fall babies, while an October birth in Australia is Springtime.