Thanks!
To recap, the reason this got stuck was that there seemed to be a bit of disagreement as to whether I should have added the yyyy-mm-dd format *alongside* the existing yyyy/mm/dd, or *replacing* it. I made my point as to why I think the former was probably a better idea, but the discussion didn't move on.
There was also the issue of me having messed with the po files, but that was already addressed (removed).