It shows a date of 7/16/2019, which is why it is showing up in the smartlist.
The issue is that it was imported 8-9 months ago.
So, it's not the smartlist, but for some reason, periodically, a chunk of my albums, a large chunk, get a new [Date Imported] field.
All my music is kept on a NAS, but I don't see why that would impact this.
This is a somewhat well known problem. What can happen is this:
1. You import stuff from your NAS.
2. Time passes. Your NAS goes to sleep.
3. MC opens and find the NAS asleep. After some timeouts occur on reading some files, MC deletes them from your library. You probably don't see this happen because...
4. The NAS wakes up. MC sees a file system event or the two timer expires.
5. Now MC sees the files that it just deleted. But they are "new" because they weren't there during stage 3 above.
6. All these files (which might only be some of them, not the whole drive) are re-imported and their import date is updated to right now.
To "fix" this, I like to set two options to prevent it:
A. Tools > Options > Library & Folders > configure auto import > Tasks > Fix Broken links. Set this to NO to be the most safe. Set to "yes (protect files on missing drives)" to be nearly as safe.
B. Tools > Options > Library & Folders > configure auto import > Tasks > Update for external changes > (unchecked) . This one is related, but not strictly necessary. It tells MC to NOT re-read tags if they are changed by other applications outside of MC.
Brian.