Sorry for starting a theroy of my own Posey but your birthdays thread made me think of it.
You know the rhyme about which day of the week you were born on? In my family it seems to work, we were all born on different days and we seem to have temperaments roughly right according to the rhyme. Like I was born on a Friday and seem to be more easy-going and tolerant (sorry sis) than my sister who was born on a Saturday and does love working really really hard.
Does it work for anyone else?