Problem with bookmarks in Safari

Try deleting this file (or moving out of this folder to your desktop):

[user] ▸ ⁨Library⁩ ▸ ⁨Containers⁩ ▸ ⁨com.apple.Safari⁩ ▸ ⁨Data⁩ ▸ ⁨Library⁩ ▸ ⁨Preferences⁩ ▸ com.apple.Safari.plist

(Don't worry about breaking Safari, it will create another file next time it starts, but it won't have the corrupt date in).

After I did this I was able to delete bookmarks again. It did ask that question again on the first delete, but this time round when I clicked "Don't Keep" it actually worked.

I had this problem with Firefox and it was a year 4001 date. I spent hours on this and tried all the other suggestions I could find on the web, short of re-installing MacOS, but nothing fixed it. Then I searched every file connected with Safari and found this one with the corrupted date embedded.

Safari now runs fine for me with no trace of the link back to those stubborn imported bookmarks. I hope it works for you.

Sorry that didn't work for you. I know there are different folder structures in different versions of the OS but I'm not an expert. The next thing I would try is to find every instance of the file com.apple.Safari.plist anywhere within your library folder. Strangely I found more than one in various folders but only one contained the corrupt date that causes this problem. Selectively remove/replace each one until you find the culprit. I found the problematic one by previewing files and looking through them until I saw the rogue date. It could even be a different file in your version, but the file com.apple.Safari.plist did crop up a lot in other answers to this question that appeared in my searches, though they had it in a different sub-folder.

It's important each time, before you remove the suspect file, make sure you have first fully Quit out of Safari. The cure works because when it opens it looks for that file, doesn't find it, and creates a new one which is good.

If that doesn't work I'm sorry I have no other suggestions. Good luck.

Please post the version of Safari and macOS installed on your Mac.

Go to Finder and select your user/home folder. With that Finder window as the front window, either select Finder/View/Show View options or go command - J.  When the View options opens, check ’Show Library Folder’. That should make your user library folder visible in your user/home folder.  Select Library. Then follow the above.

You are welcome. Glad to help.