Let's say, someone grew up in an orphanage in the 1940s with an unknown date of birth. This was before any computer systems and the date would have been recorde

Let's say, someone grew up in an orphanage in the 1940s with an unknown date of birth. This was before any computer systems and the date would have been recorded on punch-card, probably in 2+3 digits, here defaulting to `00` for the year for a missing value. It's plausible that this would have been transitioned as-is to any more modern date encodings.