For most people, exact time doesn’t even really matter — it’s about estimating a broad chronological context for the most part. I’d just wish the UI would have a universal and easily accessible way to disclose the exact time when I actually need it.
But that is throwing out the baby with the bath water. The existence of multiple locally used data formats is no reason replace information with this oversimplified nonsense. Browser can and used to provide the locale with every request. That is enough information to format a data such that it is readable to the user.
Citing RFC 3339 is usually a better idea, since in addition to be readable for free, it is limited to the date formats you are thinking about. My 2 cents on your preferred citation, keep preaching though!
https://datatracker.ietf.org/doc/html/rfc3339
With apologies for the delayed response, I got here from the weekly hackernewsletter.