I was about to write that surely, that only applies to the OCR section printed on the physical passport, but if I read ICAO 9303 correctly, it's the other way r

I was about to write that surely, that only applies to the OCR section printed on the physical passport, but if I read ICAO 9303 correctly, it's the other way round - the OCR section can include either a four-digit year or a two-digit year, but the chip has only six bytes for the date of birth, representing YYMMDD in digits (plus special characters for an unknown or partially known date of birth). Edit: apparently there's an optional section in the chip (data group 11 or DG11) that allows for longer-form data than the ancient machine-readable format, including non-latin letters in the name and a birthdate including the century. I don't know how widely used that is though.