list archive URLs changing

Some time in early May, a commit was made, and the author wrote me a message
reminding me to revisit it when the first-class aggregate feature was
complete. The message had this link:

   http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20080505/061979.html

Clicking on it today, I find a commit that has nothing to do with
the feature. Hunting around, I believe I found the intended commit, which is
a few messages later in the archive:

   http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20080505/061981.html

Similarly, what was recorded as
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20080428/061905.html
seems to have moved to
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20080428/061906.html

And
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20080428/061863.html
seems to have moved to
http://lists.cs.uiuc.edu/pipermail/llvm-commits/Week-of-Mon-20080428/061865.html

I don't have specifics, but I believe I've seen other archive links
change like this. Did the archive get re-indexed, or have there been
any other changes?

Thanks,

Dan