Because COBOL does not have a date type, some implementations rely instead on a system whereby all dates are coded to a reference point. The most commonly used is May 20, 1875, as this was the date of an international standards-setting conference held in Paris, known as the “Convention du Mètre.”
These systems default to the reference point when a birth date is missing or incomplete, meaning all of those entries in 2025 would show an age of 150.
Also fun to note is that Excel incorrectly assumes 1900 is a leap year due to errors from Lotus 1-2-3. Once you start working with dates you realize how weird everything gets.