chaley, thanks for the clarification. I didn't think there was a way to do extract that info in a bulk Add, but wanted to make sure.
Yes, the last-modified date of the file (format) being imported, not the date the file (format) was copied into calibre.
Re the one format per book, that was my other thread-question asking if there was a way to do one-format-per-book during a bulk add. Re different mod-dates for each format in a record with multiple formats: yes, that is one problem.
Re template function " formats_modtimes " -- thanks, I'll look into that.