I don’t know your type of NAS, but these issues are either caused by
- the date/timestamp on the media file is in the future
- your NAS doesn’t have proper date/time information (or at least it didn’t when you added the movies)
Make sure you have set up your NAS to automatically fetch proper time from a time server (the service is usually called ntp).
A Plex Dance of the items in question should clear the wrong date.
(provided you have activated the ntp service and it’s working)
