I have just encountered a new and serious issue - after an error uploading a media file, a whole bunch of posts (about 40% of something like 450 total) have spontaneously changed their publication date to the time the error occurred.
The error was that in the process of uploading a PDF I had a momentary Wifi drop and it never reported being finished.
New posts since seem to provoke (not every time though) re-dating of additional posts as well.
I have RSS feeds so I can re-date everything but I suspect there's an ongoing problem.
I don't have any SEO kind of plugins that re-post anything automatically or anything like that, but it's a complicated multisite install with WPML and several other plugins plus Genesis and a child theme.
I know this info is pretty sketchy but I'm in production mode in the middle of an event I'm live-blogging and any hints would be appreciated.