code: @Nullable
    public static XMLGregorianCalendar getXMLCalendar (@Nullable final ZonedDateTime aBase)
    {
      if (aBase == null)
        return null;
      return s_aDTFactory.newXMLGregorianCalendar (GregorianCalendar.from (aBase));
    }
docs: Get the passed object as {@link XMLGregorianCalendar} with date and time.
  
  @param aBase
  The source object. May be <code>null</code>.
  @return <code>null</code> if the parameter is <code>null</code>.