+function room_mt:save_to_history(stanza)
+ local history = self._data['history'];
+ if not history then history = {}; self._data['history'] = history; end
+ stanza = st.clone(stanza);
+ stanza.attr.to = "";
+ local stamp = datetime.datetime();
+ stanza:tag("delay", {xmlns = "urn:xmpp:delay", from = muc_domain, stamp = stamp}):up(); -- XEP-0203
+ stanza:tag("x", {xmlns = "jabber:x:delay", from = muc_domain, stamp = datetime.legacy()}):up(); -- XEP-0091 (deprecated)
+ local entry = { stanza = stanza, stamp = stamp };
+ t_insert(history, entry);
+ while #history > (self._data.history_length or default_history_length) do t_remove(history, 1) end
+end