Belated happy birthday! Probability is based on random occurrence and, although I understand what you're getting at, probability doesn't apply to predictable events. But if we assume that chance does apply, then we would say that there's a chance of 12/365 that particular date coincides with a full moon, because there are 12 in a year (hence the word "month"), and a chance of 1 in 7 for the day of the week. So total "probability" is 12/365*1/7=0.47%. The next time you'll see a full moon on your birthday is 2041, and it actually is on 14 June, which is a Friday. So the moon will be approaching full on the Thursday. I was born on a Good Friday, and my birthday hasn't fallen on Good Friday since, as far as I can remember, although it's been very close.