Saving a CSV is changing the dates from 19XX to 20XX

Question

I'm working in Excel for Mac Version 16.106 (26020821).

I work in events where we have competitor lists that include Dates of Birth, although this issue would be relevant to anyone working with dates.

While I'm working in the original CSV document, exported from our registration platform, the dates look fine. If I save the document, keep it open, and continue to work in it, the dates are fine. However, as soon as the document is closed and re-opened (or closed and used as part of a Terminal command), any date (year) starting with a 19XX will change to 20XX. So a DOB of 6/30/80 (46 years old) will change to 6/30/2080.

This is wreaking havoc on our events, showing people's ages as -66, since our bracketing system dynamically shows age depending on DOB.

Answer 1

See whether the Preferences at Excel> Preferences> Edit — Date Options can help.

Answer 2

Changing the format of the date to XXXX-XX-XX before saving has fixed the issue. Kind of a pain, but there ya go.