100% but "Completed on" tab is blank

[Blinding]

Sometimes I wind up with a torrent that is 100% but the completed on date is missing. This is annoying as I sort my torrents using that tab. Where does utorrent get that date?

This typically happens when I have been mucking about moving files and such. For example just now I reinstalled utorrent and then re-queued the torrents that I had files for. It correctly noted that they were in the completed directory, ran a recheck, and marked them as 100%. But only half of them wound up with completed dates. I don't see any pattern as to why some did and some didn't.