I've seen lots of %Y%m%d on filenames timestamped by humans. People timestamp stuff for different reasons. If you do it to avoid collisions then adding sub-sec

I've seen lots of %Y%m%d on filenames timestamped by humans. People timestamp stuff for different reasons. If you do it to avoid collisions then adding sub-second precision makes sense, but in many contexts second or even day precision is all you care about. The important point is that %Y%m%d%H%M%S is human parsable and still sorts correctly (though humans typically prefer %Y-%m-%d %H:%M:%S for readability)