> "I store all dates in spreadsheets in ISO format"
As in SQL, the application’s native date format (which is usually a number with appropriate format) would be the natural choice and a YYYY-MM-DD string would be a distant second. ISO (presumably, 8601) format is too broad, and admits of a mix of formats that are not simply sortable (quick, which is first 2021-W14-2 or 2021-04-07?).
Eh, when people say ISO they mostly mean YYYY-MM-DD.
If a date is going to be string prepended to something else, or if the spreadsheet is going to be exported to CSV, or parsed by some tool, then storing dates in YYYY-MM-DD can be a very justifiable thing to do in a spreadsheet.
Also Excel likes to format dates using the system locale, which is, well, stupid. So I have to enter YYYY-MM-DD as a custom format anyway, or change the locale on the column to China. (Or Cherokee, who apparently also properly format their dates!)
(Also Excel is smart enough if you set a column as YYYY-MM-DD custom format, it'll let you use all the date based pivot table stuff as expected)
He was a radical honestly type guy. It was all on the table and we had lots of success stories. We would give anyone a chance which let a lot of self taught, entry level people get work. I got a ton of experience mentoring people, as well (difficult people, too). Unfortunately, he got screwed over by a shotgun clause in a business agreement and lost the business that to an ex-partner. That's what led me to my current job, though, where I've been happy for over 10 years and it's much more stable.
If he had said anything other than "in sql" it would be the correct answer.
"I store all dates in spreadsheets in ISO format"
"I prepend ISO dates to marketing campaign names so I can easily sort them in the horrible web frontends that doesn't have a sort by date option"
"I start all my blog entries with ISO dates..."
I mean, just... so close!