Law: What happens if you don't know your date of birth?

I’ve been searching online but didn’t find anything. It has to have happened at least once in the recent past - a baby was found abandoned, the mother is never found or identified, and nobody knows the baby’s exact date of birth. How does the LAW handle this, when that baby (and later, the adult) needs to go through the bureaucracies of life? E.g., temporal legal questions such as determining whether or not they are older than or younger than a cutoff date to begin kindergarten, determine when they can get a driver’s license, when they can legally drink, legally vote, or who they can legally have sex with without either partner being guilty of Statutory Rape, as well as simply being able to get through life where standardized forms have a “date of birth” field?

E.g.: "Ladies and gentlemen of the jury. Regardless of whether or not a statutory rape occurred as a matter of law is not at all clear, because my client was a foundling and the “birthdate” that he uses is only an approximation, and so it may in fact be the case that he was still under 18 when he had sex with that girl. Therefore, you cannot find him guilty beyond a reasonable doubt of being a person 18 or older having sex with an underage person.

Can the person (or the foster care system/orphanage/whatnot) simply select a date? Can it be changed later if the person wishes to have a different birthday (or does the “previously chosen” one become fossilized as a matter of law), or if they uncover evidence that the current date used is not likely? (e.g. a foundling where the foster care system “chose” a birthdate of April 5 tracks down their biological father through DNA testing, and the father reveals that, way back when in the year the child was probably conceived, he was only sexually active with local women during the wintertime because in spring, summer, and fall he was working overseas, indicating that a Fall birthday would be more likely.)

Obviously, this is not a question for specific legal advice.

I know that my grandmother and her younger sister were both legally the same age, even though her sister was actually a year younger. The story I was told was that when they were born in extremely rural Arkansas in 1910/1911, there were no birth certificates and their mom ran off with the family bible at some point ( Seriously. My great-grandparents married-divorced-married-divorced, and then my great-grandmother ran off to Utah in the 1910s). This only ever mattered when they applied for social security numbers as adults, and I think the SS people basically took them at their words. For reasons that were never made clear to me, my aunt wanted to be a year older than she was in reality. With no contesting data, one year older she became.

Here are the birth certificate rules from the state of Oklahoma:

So it sounds like you make your best guess, and if the actual information is found, it replaces the guess.

I have also heard about refugees and others from locations where their birth date was not recorded being allowed to choose their own date for identification purposes.

In NY, the social services district chooses an approximate date of birth and files a report with the Dept of health/registrar of vital statistics .That report becomes the birth record, and presumably functions as a birth certificate. If the child is later identified and a birth certificate has been previously filed or is filed after the identification, the social service report is sealed.

Do they simply start using a birth date of their selection and, eventually, it becomes incontrovertible as a matter of law when the refugee becomes recognized generally as having that birthdate (kind of like how, in many areas, a person can change their name legally by simply being known generally under that name), or do they have to apply to a court, the immigration office, or local social services for a certificate of declared/adjudicated date of birth?

I don’t see the law reacting too kindly to just allowing refugees to use whatever DOB they feel like that day (e.g. tell the DMV that they were born on February 1, 1975, tell the IRS that they were born on December 20, 1974, and tell the passport office that they were born on March 7, 1975), so I would imagine that they have to standardize on a date somehow.

My grandmother thought her birthday was April 24 her whole life until she looked at her birth certificate when she was in her 80s and it said April 23, so it apparently doesn’t matter too much on forms with a DOB field. Of course most of the forms in her life were filled out prior to computerization, but she did work on the Manhatten Project and it didn’t raise any red flags during that.

A couple of answers that are rather tangent but somewhat related. There is a French film by , Netflix: Ousmane Sembène *Mandabi * where this plays an important part in the plot. The man needs a birthday to get proof of birth to cash a check or some such.

I was in a village in Western Alaska where they were celebrating an old ladies birthday. The press asked the usual “To what do you attribute your long life”. The old lady answered in some native language and the crowd found it quite amusing. The translator told the press that she attributed her long life to eating only fat salmon and no alcohol. Later I ask my friend why the crowd thought that was amusing. My friend said what she had really said was that she attributed her long life to her group [tribe] not having a calendar. [She apparently gave this answer each year and the press never figured it out, or didn’t care.]

In her 70s, my mother needed her birth certificate to get a passport. She discovered that the certificate’s date of birth was two days later than the date she had always celebrated. The probable reason was that back when she was born, in 1913, the doctor would go around the neighborhood, delivering babies, then at some point turning in several days worth of data. So all the babies for that period were given the same date of birth. Apparently, this kind of thing was very common back when most babies were delivered at home.

And it’s very possible that the doctor may have been using a Hebrew calendar, which would complicate matters.

My brother was born in CAnada 90 some odd years ago. I do not know why mom was in Canada, but she thought the Dr. would fill out the birth certificate when it was her responsibality. At the out break of WWII my brother tried to inlist in the US Navy. He said that it really caused him a lot of problems to inlist. The Navy was not sure they could take him, the Army had the same problem and the Draft Board thought he was just trying to advoid the draft and wanted to arrest him. He had to get all his school records. letters from family members. Finaly the Navy agreedd that he looked the right age to inlist and he joined up.

Anecdotal, but my WAG in the case of no birth certificate, they pick a date for immigration purposes and that’s the “official” birthdate for most purposes. In one place where I worked, your birthday was a paid holiday, but you had to take that holiday during the same pay period that it fell. My birthday is in the first week of January. A large number of our SE Asian immigrants of a certain age and most of our NE African immigrants as a whole used January 1 as their official date. Made it rather difficult for scheduling purposes.

My grandparents were all born in Eastern Europe or Russia and had no birth certificates and didn’t really know within a year when they were born. Didn’t seem to matter though. They never got passports and things were much looser in those days. They just picked a birth date (or were given it at immigration) and stuck to it.

IIRC we don’t know J.S. Bach’s or Beethoven’s birthdays for sure, but we know from German parish records when they were baptized, and those dates are used by historians and music lovers to mark the date.

My mother went for a drivers license and they asked for birth certificate. She had a lot of trouble getting it and found she spent her life celebrating the wrong date. She was actually a month and 2 days younger than she thought. Record keeping in 1923 was not so good.
She also found out her official name was Roslyn nor Rosalie like she went by all her life.