If this has already been reported then I apologise. I've noticed this behaviour in KTorrent 4.2.x and 4.3.x, on Linux Mint 14 KDE. How to reproduce:

1. Create a torrent from some content, and save the torrent file.
2. Remove the torrent entry from KTorrent but keep the data.
3. Open the previously created torrent file, and set the download location to the parent of the directory holding the content (assuming the content is in a directory).

KTorrent will do a data check on the existing content, and when finished will report time seeded as >20,000 days. If the option "Skip data check" is selected, the data check obviously does not happen and the "Time seeded" starts from zero as expected.

Many thanks.

Please file bug reports at bugs.kde.org, where they can be tracked better by the developers.