What about this one?
lib.lastchange = COA_INT
lib.lastchange.5 = CONTENT
lib.lastchange.5 {
   table = tt_content
   select {
     orderBy = tstamp DESC
     max = 1
   }
   renderObj = TEXT
   renderObj {
     field = tstamp
     strftime = %d.%m.%Y
     wrap = aktualisiert am: |
   }
}
Tomas Mrozek