If it’s not in the metadata of the file, then it’s possible that something screwed up and the “date added” field in the Plex database populated with an impossible date. A Plex dance should fix the files to get the correct “current” date. Be aware that doing the dance will cause the files to appear to still be “recently added”, but they should not longer stick to the front of this list in front of other “new” files.
Someone in the past had this happen. They manually edited the “date added” field in the Plex database itself. Very scary sounding, but if you are proficient enough and willing to try, you can search for the topic. I’ll give the search a try myself, and edit this if I find the post.
Edit: Aha. The first post I found mentioned that Plex picks the date the files were “created” or “modified” (unsure which one) on the filesystem. So in Linux, he did a “touch” on the files to update the date of the files to be the present date, and Plex picked up the new date and fixed it on their end.
The following post seems to suggest that Plex respects the filesystem “date” when it pulls the file in, but then never updates that date afterwards. They used a SQL command to fix the dates, but it’s a bit over my head to interpret it. If you are SQL proficient, then consider reading this post:
