Previously the "weekly" archives only used the creation date of the post to determine which "weeks" to link. Now they use the display date so that if one uses the rewrite history feature to back-date posts, the archives lists will now reflect this properly.
(note: I say "weekly" since that archive style is not truly weekly, but rather a method of slicing up months which tends to slice into 7-day segments. I really should add a true weekly archive option, which aligns on Saturday-Sunday borders.)