Please excuse me for my bad English. Feel free to re-write this entry.
In eswiki we have a maintenance category that uses timestamps as sortkeys, articles with older timestamps appearing first. It was working ok until a few days ago when some changes were made (see this comment by Bawolff [https://bugzilla.wikimedia.org/show_bug.cgi?id=4912#c19]). After that, we experienced two different issues:
- Articles that have been moved during the three last days, are completely mis-sorted, appearing at the very end of the category under their initial letters. It looks like their timestamp sortkeys have been lost, and only their pagenames are taken.
- This issue can be easily fixed, nevertheless I'll describe it fyi:
Articles with 8-digit timestamps YYYYMMDD (usually manually tagged by users) and those with full-sized 14-digit timestamps YYYYMMDDHHMMSS (usually bot inputs) are no longer correctly sorted each other. In addition, we created some "label" pages to mark months and years boundaries, keyed with 6-digit and 4-digit timestamps. Right now, these labels appear at the end of their periods, rather than at the beginning. I plan to fix this issue padrighting all timestamps with zeros up to 14 digit.
- Yes, a third issue appeared: Pages with pure-numeric pagenames are also mis-sorted. Our "label" pages assigned to mark years are titled Wikipedia:2007, Wikipedia:2008 and so, and are manually sortkeyed with 2007, 2008 and so. It seems these pages are experiencing another kind of sort error, appearing all together after all timestamped pages but before moved ones. The issue disappears adding a letter (not a number) to the sortkey, ie 2007x.