[Zope] dtml-calendar error on Zope 2.6.2

Hi all, on Zope 2.6.2 (win 32) this code (works well in Zope 2.5.1) <dtml-calendar> <dtml-var date fmt="%d"> </dtml-calendar> gives this error: Error Type: KeyError Error Value: mese_prec Traceback (innermost last): Module ZPublisher.Publish, line 98, in publish Module ZPublisher.mapply, line 88, in mapply Module ZPublisher.Publish, line 39, in call_object Module OFS.DTMLMethod, line 126, in __call__ Module DocumentTemplate.DT_String, line 474, in __call__ Module Products.Calendar.CalendarTag, line 930, in render KeyError: mese_prec Can you help me? thanks mic