def _CalculateDOWDelta(self, wd, wkdy, offset, style, currentDayStyle):
        """
        Based on the C{style} and C{currentDayStyle} determine what
        day-of-week value is to be returned.

        @type  wd:              integer
        @param wd:              day-of-week value for the current day
        @type  wkdy:            integer
        @param wkdy:            day-of-week value for the parsed day
        @type  offset:          integer
        @param offset:          offset direction for any modifiers (-1, 0, 1)
        @type  style:           integer
        @param style:           normally the value
                                set in C{Constants.DOWParseStyle}
        @type  currentDayStyle: integer
        @param currentDayStyle: normally the value
                                set in C{Constants.CurrentDOWParseStyle}

        @rtype:  integer
        @return: calculated day-of-week
        """
        diffBase = wkdy - wd
        origOffset = offset

        if offset == 2:
            # no modifier is present.
            # i.e. string to be parsed is just DOW
            if wkdy * style > wd * style or \
                    currentDayStyle and wkdy == wd:
                # wkdy located in current week
                offset = 0
            elif style in (-1, 1):
                # wkdy located in last (-1) or next (1) week
                offset = style
            else:
                # invalid style, or should raise error?
                offset = 0

        # offset = -1 means last week
        # offset = 0 means current week
        # offset = 1 means next week
        diff = diffBase + 7 * offset
        if style == 1 and diff < -7:
            diff += 7
        elif style == -1 and diff > 7:
            diff -= 7

        debug and log.debug("wd %s, wkdy %s, offset %d, "
                            "style %d, currentDayStyle %d",
                            wd, wkdy, origOffset, style, currentDayStyle)

        return diff
Based on the C{style} and C{currentDayStyle} determine what
        day-of-week value is to be returned.

        @type  wd:              integer
        @param wd:              day-of-week value for the current day
        @type  wkdy:            integer
        @param wkdy:            day-of-week value for the parsed day
        @type  offset:          integer
        @param offset:          offset direction for any modifiers (-1, 0, 1)
        @type  style:           integer
        @param style:           normally the value
                                set in C{Constants.DOWParseStyle}
        @type  currentDayStyle: integer
        @param currentDayStyle: normally the value
                                set in C{Constants.CurrentDOWParseStyle}

        @rtype:  integer
        @return: calculated day-of-week