Double crosspost to wikipedia-l and wikitech-l because this might affect
some people.
There was a bug with history paging whereby the last item of one page was
displayed as the first item of the next, i.e. the pages overlapped. This has
now been fixed in MediaWiki, and the fix will shortly be live on Wikimedia
sites. The consequence of this is that some history URLs will now be offset
by one row compared to how they were before. A link like this:
http://en.wikipedia.org/w/index.php?title=Main_Page&offset=200603200044…
...will display the items *after* 2006-03-20, 00:44:34 UTC, *not* inclusive
of that date, whereas before the fix it would have displayed items inclusive
of that date.
The reason for the change is that if we kept the same URL scheme, in some
cases, it would have required an extra database query to work out the
correct offsets for the prev/next links. Using non-inclusive offsets, all
the data is available already.
-- Tim Starling