Wouldn't it make sense if the content of it could be auto-generated as well for the users' locale directly with no need for JS?

Either as a date in the example "4 days ago" or "in 2 days, 2 hours and 28 seconds" for future events. This requires some control for granularity to control for how precise you want it to be and what to omit.

"a few seconds ago", "3 seconds ago", "less than a minute ago".

Should support a shortform that can act as a countdown timer "00:00:56" or "00:56".

It's wild to me that it doesn't even generate a tooltip by default.