[glenm125]

First, thanks for cedhax for posting this thread in response to my original comment elsewhere.

Originally Posted by kovidgoyal

You want a last modified date for the individual e-book files or the overall book metadata? In which OPDS feed, the acquisition feed? In what format?

I'm not expert in the OPDS format nor nomenclature, so let me instead describe from a user point of view what I want to achieve.

Part of what I read in Calibre and related readers is fanfiction. As authors extend those stories with new chapters, I use fanficfare to generate epubs from content of those sites into my calibre library. I presume this updates the metadata (file size, date, 'completed' tag, etc), perhaps also updating author (if author changed his name, not an uncommon thing!). As well of course as replacing the epubs.

Whether a new version or not has come, I might have also updated the metadata, eg with a rating or additional tags.

So it would seem to me that it would be useful to have latest updated date for metadata, and latest updated date for each file, assuming the OPDS format supports both. That provides most visibility into change in downstream tools.

This would allow a reader application to know when to merge metadata changes in, and whether to flag a book (otherwise thought to be read in the client) as now unread (because it has changed). And even show how much longer the book is compared to the read content (new content length less length when last read).

But again, I'm not expert in the formats or established usage paradigms of this content. Library and reader authors should probably comment on what would help them most.

Hope this helps,

glen