diff --git a/src/calibre/library/server/opds.py b/src/calibre/library/server/opds.py
index 43cde646c6..41d3654890 100644
--- a/src/calibre/library/server/opds.py
+++ b/src/calibre/library/server/opds.py
@@ -205,19 +205,24 @@ def ACQUISITION_ENTRY(item, version, db, updated, CFM, CKEYS, prefix):
     idm = 'calibre' if version == 0 else 'uuid'
     id_ = 'urn:%s:%s'%(idm, item[FM['uuid']])
     ans = E.entry(TITLE(title), E.author(E.name(authors)), ID(id_),
-            UPDATED(updated))
+            UPDATED(item[FM['last_modified']]))
     if len(extra):
         ans.append(E.content(extra, type='xhtml'))
     formats = item[FM['formats']]
     if formats:
+        book_id = item[FM['id']]
         for fmt in formats.split(','):
             fmt = fmt.lower()
             mt = guess_type('a.'+fmt)[0]
-            href = prefix + '/get/%s/%s'%(fmt, item[FM['id']])
+            href = prefix + '/get/%s/%s'%(fmt, book_id)
             if mt:
                 link = E.link(type=mt, href=href)
                 if version > 0:
                     link.set('rel', "http://opds-spec.org/acquisition")
+                    fm = db.format_metadata(book_id, fmt)
+                    if fm:
+                        link.set('length', str(fm['size']))
+                        link.set('mtime', fm['mtime'].isoformat())
                 ans.append(link)
     ans.append(E.link(type='image/jpeg', href=prefix+'/get/cover/%s'%item[FM['id']],
         rel="x-stanza-cover-image" if version == 0 else
diff --git a/src/calibre/srv/opds.py b/src/calibre/srv/opds.py
index e5e8e95c1e..a1e50306e6 100644
--- a/src/calibre/srv/opds.py
+++ b/src/calibre/srv/opds.py
@@ -198,16 +198,22 @@ def ACQUISITION_ENTRY(book_id, updated, request_context):
         extra.append(comments)
     if extra:
         extra = html_to_lxml('\n'.join(extra))
-    ans = E.entry(TITLE(mi.title), E.author(E.name(authors_to_string(mi.authors))), ID('urn:uuid:' + mi.uuid), UPDATED(updated))
+    ans = E.entry(TITLE(mi.title), E.author(E.name(authors_to_string(mi.authors))), ID('urn:uuid:' + mi.uuid), UPDATED(mi.last_modified))
     if len(extra):
         ans.append(E.content(extra, type='xhtml'))
     get = partial(request_context.ctx.url_for, '/get', book_id=book_id, library_id=request_context.library_id)
     if mi.formats:
+        fm = mi.format_metadata
         for fmt in mi.formats:
             fmt = fmt.lower()
             mt = guess_type('a.'+fmt)[0]
             if mt:
-                ans.append(E.link(type=mt, href=get(what=fmt), rel="http://opds-spec.org/acquisition"))
+                link = E.link(type=mt, href=get(what=fmt), rel="http://opds-spec.org/acquisition")
+                ffm = fm.get(fmt.upper())
+                if ffm:
+                    link.set('length', str(ffm['size']))
+                    link.set('mtime', ffm['mtime'].isoformat())
+                ans.append(link)
     ans.append(E.link(type='image/jpeg', href=get(what='cover'), rel="http://opds-spec.org/cover"))
     ans.append(E.link(type='image/jpeg', href=get(what='thumb'), rel="http://opds-spec.org/thumbnail"))