n. Informal a happy, satisifed person (esp. in the phrase not a happy camper)

What do you call a person who has the same birthday as you?

Birthday twins. I have no citation, but have often heard this used to describe exactly what is asked: two or more, not necessarily related, born on the same day, regardless of year born. Other forms of the same construction are astro twins, astrology twins, and star twins.

What is a birthday twin?

birthday twins (born on the same day & same month) birthdate twins (born on the same day & same month & same year)

What is the closest two babies can be born?

The mother had the first child at 25 weeks of pregnancy in early December 2011, and the next child at 29 weeks of pregnancy in early September 2012, the Telegraph reported. Irish twins is the term for siblings born in the same calendar year or within 12 months of each other.