Inbuilt non-user-defined columns
 

Hi, can you please point me to where those fixed non-user-defined columns are explained in details, where I could find what exactly does (and what doesn't) update the individual permanent columns?

The column header pretty much says what they are for.
They are based upon Dublin Core (DC) matadata
Calibre adds a couple for the user
{date} is the date the Record was made
{id} is the serial number Calibre adds to make sure the details match the book saved (If you peeked beneath the skirts :eek: tou will notice they all are title (##) That ## is the ID
{rating} a place (stars) where users score the book
{tags} Any keyword list you want to assign to help select the book. Common is genre
{last_modified} ANY change made to the metadata used in Calibre

Thanks theducks, it was the Modified {last_modified} column I was not sure about. I wanted to know what I'm allowed to do before the record is updated and where to find this information.
You say ANY change... It means that if my record was last modified e.g. on 10 Jan 2018 when I edited the epub, and today I insert a comma in the Title column I found missing in the name of a book, the important date 10 Jan 2018 will be updated and lost because of this unimportant comma, and I cannot do ANYTHING about it except stop using this column completely.
It is quite useless column because initially EVERYTHING there has the same date as the Date {date} column even though the record was actually never modified...
Fortunately I can create my own column called e.g. Edited which will keep the date I want there.

Initially last_modified recorded the creation change. So It is the same as date.
When you added the comma, you 'dirtied' the metadata status (and a backup OPF is queued.

I also have #edited, #done (reading) and #VC (valid checked)

last_modified is changed when any of the following happens:

• Book record is created for the first time.
• Metadata of the book is changed (this includes cover).
• A new format is added to the book record.
• Format(s) deleted from book record.
• A book format is edited by calibre editor.
• Renaming an item (e.g tag) in the tag browser will update the last_modified column for all books containing the renamed item.
• Deleting an item (e.g tag) in the tag browser will update the last_modified column for all books containing the deleted item.
• Creating/modifying/deleting a custom column will update the last_modified column for all books in library.
• Changing the template for a composite column will update the last_modified column for all books in the library. (There is a way to prevent this mentioned by @chaley but I forgot how to do this)

Edit: if you want more control over last_modified, you can try the Last Modified plugin which updates custom date column based on selected events.

Edit2: The builtin last_modified has to be this way because it is used to update caches.

Thanks for your clarification theducks, I agree, but I was wondering - some of the those columns you mentioned can only be updated manually, however, out of them the #edited one could also be triggered automatically, perhaps from the conversion or some other procedure which would indicate there really was some serious modification carried out. Any idea how to do it easily?

FWIW - I have #lc_date and #lc_what columns ('lc_' last change) that I maintain manually, via F2 in the book list. The #lc_what column is a tag-like column.

BR

Thanks everybody.