Dating someone with your same birthday
For example, we could look at similarities in names, employment history, appearance, etc.
The larger you cast the search, the more possible bases there are for finding coincidences.
If you add in year, it's probably something like 1 in 3000 or 4000 (most people have relationships with people relatively close in age). That is, if you had asked, before meeting your current boyfriend "What are the odds that the next man I have a relationship with will be born on same day and year? However, post hoc (that is, while in the relationship) it's trickier because you would have noticed a lot of coincidences too: My boyfriend was born the day before me!
My boyfriend's mother has the same name as my mother! The odds of "some weird connection with my boyfriend" are impossible to calculate.
We've argued before about the probabilities and I am still not satisfied.Please note: The suggestions and advice offered on this web site are opinions only and are not to be used in the place of professional psychological counseling or medical advice.If you or someone close to you is currently in crisis or in an emergency situation, contact your local law enforcement agency or emergency number.Next one should figure out what the chance is of being born in the same year.Just to give an impression of this chance I'd start with the rule of thumb as presented by xkcd which gives a dating age range of $\pm \ age-\frac 7$, where age $=$ age you started dating. However, the chances of dating someone from the exact same year are far greater due to a flaw in the educational system where pooling is done by the date of conception.