Mayan Theory correct for anyone????

Sarah
The Mayan Theory says if you add your age at conception to the month of conception and get an even number your having a GIRL and odd numbers mean a BOY!  
I was 24 and conceived in September (9) for my first and it was a boy.  This pregnancy I'm 31 and conceived in November(11) which indicates a girl.
Has this Theory been correct for anyone else???