[Arrghus]

I was trying to work out how to add a custom metadata field to an eBook. This led me to searching on the internet for help, and stumbling across Sigil. I booted up this application and looked at the metadata of various books and was surprised to find that there are many more fields than what is shown in Calibre.

I want to be able to display and edit the original published date of my books, as well as the publication date of a particular edition (which is what is usually shown under 'Published').

How can I get these extra fields (such as 'Usage Rights' among others) that can be edited in Sigil to show up in Calibre? I'd MUCH rather do my editing directly within the program itsel! (Sigil is a little scary to the novice.)

Many thanks,
Thomas

EDIT:

I think I'm beginning to realise that Calibre isn't actually altering the metadata of my files at all - Calibre makes changes to the database but not the files themselves, right?

Another question: If I edit the metadata of a book in Calibre, can I revert back to the metadata stored in the file itself?