Astrology is obviously nonsense, but it seems plausible that the season of birth could have a personality effect: the cold dead of winter, with little fresh food vs spring etc, also from the attitudes of surrounding adults.

Of course, different near the equator, and phase-shifted in the southern hemisphere, and... much less pronounced in modern times, with supermarkets, refrigeration, air-conditioning/heating, imported foods, and wider social presence (newspapers, TV, radio, internet, phone) etc.