Your age is very important in Austria. Persons older from 18 years are “adults”. Children and adolescents are “minors”. Children and adolescents are treated differently than adults. Please say the truth about your age.
Every date from another calendar can be converted.
The police will do so.
Some children do not have a document to show their age. Their age will be estimated. They have to go to an “age assessment”.
Age assessment means: A doctor will do a medical examination to see how old a person is. Your arm and teeth will be X-rayed and your body will be examined.
You don’t want to take off your clothes in front of the doctor? Nevertheless please go and see the doctor. Tell him if you don’t want to take off your clothes. This will not result in any negative consequences.
The doctor will inform the Federal Office for Immigration and Asylum about the result. The Federal Office for Immigration and Asylum will inform you if you are a minor (under 18 years) or if you are an adult (over 18 years). This is how old you are for the Austrian authorities.
If you are an adult (older than 18 years), you will be treated differently. You will live in houses for adults. You may have to go back to another country of the EU (Information about the Dublin Regulation).
Maybe you think this age is wrong. As soon as you get a first decision in your asylum procedure, you can say “no” and appeal against the result of your age assessment.