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.
Well, looked it up and it wasn’t SPSS I was thinking of, seems they use 1582 and count to by seconds which results in pretty absurd intergers. And STATA arbitrarily uses 1 Jan 1960 because why not.
Honestly your version sounds cooler. I use R now for my data needs, and looking is up, those badasses do use 1 Jan 1970. Why anyone pays for statistical software when we have R and Python, I’ll never understand.