Henry Chapman

There were a bunch with just a date, no time, all the same: date-added = {2004-01-01} and otherwise with capitalized PM, such as this: date-added = {2026-10-24 2:53:06 PM +0200}

Yes, that version works! It shows the Added dates in my original bib file. At least it does for those that have presumably well formed dates in that file on a 24h clock. Newer references that I added in the last month are blank. Those have "AM" or "PM" in the time (uppercase). In a test file I made with "pm" (lowercase) the date showed in the column. But I can fix those references and I would say the problem is solved.

I tested it, but it could not open any .bib file - I didn't throw any error that I could see, but it didn't do anything. I could create a new bibliography, but that was unresponsive to adding a new bib file to it. I created an entry by hand, saved the file, and it couldn't read it back. The new saved file, however, did not show "am" in the time.

Yes, very weird and driving me crazy! I tried changing the date format in System settings. The format in the bib looks e.g like date-added = {2005-10-11 08:39:45 -0700} When I add a new item to the file, it shows today's date in the column, and this is saved in the bib file: date-added = {2026-10-24 5:36:35 pm +0200}, OK, so I just added "pm" to the old date (date-added = {2005-10-11 08:39:45 pm -0700} and it worked, so you might be right and that at some point in the past I had a 24h format

Blank Date-Added column