This isn’t particularly useful, but if you’re like me it’s nice to have someone wish you a happy birthday. Trust me. After a certain age, the only person who really remembers your birthday anymore is your mom. Maybe your husband/wife or girlfriend/boyfriend, if you have one.
Just tell Siri your birthday. For example, “My birthday is [month][day].” That’s it. Now Siri will wish you happy birthday when that special day comes. That’s nice. At least someone out there will wish me a happy birthday!
For more fun, try to tell Siri that it’s your birthday on that day. See what she does.