The point is that both are technically correct. At 12:00am on January 1 that happens to fall on a Monday something that occurred 1 second ago can be considered to have taken place: last week (depending on when you consider weeks to start/end), last month, last year, yesterday, etc.
Sure, they’re both technically correct, but that wasn’t the question. The question was
> Where have you seen a service describing something posted less than 12 hours ago as being "posted last week" rather than "posted yesterday"/"posted today"?
Every single time display library I have seen will do as the poster explained, and show more granular information the closer it is (generally starting at “X seconds ago”). Your technicality is certainly true, but a strawman.
Actually, it's that question that is the straw man. jstanley's point is that to the reader "posted last week" could mean almost no time at all ago. It's not about the display library choosing to label recent things as this. It's about humans reading such a label and not receiving the intended information, because humans don't cut off what they understand "last week" to mean at some arbitrary 12-hours-ago mark.
Except they do get the intended information. The label doesn’t exist in a vacuum; the user would have seen other examples showing the specificity at intervals other than “last week” which sensitizes them to the cutoff points.
This is literally a non-problem. If a library behaved in the way the parent commenter makes them seem like, then, sure, they have a point. But they don’t. Something that occurred a second ago would say “a second ago”. Something that occurred 5 minutes and 43 seconds ago would say “6 minutes ago”, etc. There is no library in the world which takes a timestamp a second ago and outputs “a week ago” and pretending like there is is, literally, a strawman.
Yeah, I've seen enough examples to know that no 2 websites implement the same logic so I shouldn't try to second-guess anything more than what the text literally says.
But… users don’t. Literally no library out there does what the parent commenter claims they could do. They all use sensible cutovers for relative dates.
The point is that if a user sees "last week" it's ambiguous. They DON'T KNOW that your libraries don't behave that way. All they see is "last week". Are you really not getting this?
