Datebirth is not a valid date (age must be over 18) help me

Help me i can not fill in the form. All information what i writing is corect.
write an example. in which format to write the date of birth!
1900.1.1 or 1900 \ 1 \ 1 or 1 \ 1 \ 1900 or 1.1.1900
please !!!

Hello there,

It should be written in Year-Month-Day type - I.e. 1900-01-01

Even I had this problem, you are actually supposed to write it with dashes(-) in between instead of slashes(/) or full stops(.). e.g. 1900-01-01