Why have my folder modification dates changed in bulk?

I just noticed today that the Finder has changed the folder modification dates of just about every folder I have under Documents (which is synced to iCloud). It appears that every folder with a modification date older than September 16th 2022 got changed to show a modification date of exactly that date at the same time. Folders that were changed after that date seem to have retained their modification dates. As I was looking through folders, I could in some cases literally see the modification dates changing in the Finder before my eyes as the previous dates disappeared from view. I see the modified dates on *both* my computers, so I'm guessing it was some sort of change on the iCloud server side. The modification dates of actual files seem unaffected (thank goodness), as do the folder modification dates of any folders outside of iCloud.

This just seems very weird, and of course annoying because it's helpful to be able to see the (actual) modification dates of folders. I came across a thread (which I can now no longer locate) which seemed to suggest this sort of thing can happen when Apple updates/replaces their iCloud servers, but I'm hoping someone here can offer some insights as to whether I can get my real modification dates back (I haven't tried pulling folders back from Time Machine, but I think I'll try that next).