What happened in March?

If you are part of any social or professional network which shows upcoming birthdays of your friends, would you check and let me know if you don’t see any disproportionately large number of birthdays in December/January? I always notice this and wonder why. Is it phenomenon India specific or global? Something to do with weather or end of education and fiscal year? I could do some research with monthly birth data worldwide but I am too lazy for that.