def select_prev_day(self):
        """Updated calendar to show the previous day."""
        if self._selected_date is None:
            self._selected_date = datetime.datetime(self._year, self._month, 1)
        else:
            self._clear_selection()
            self._selected_date = self._selected_date - self.timedelta(days=1)

        self._build_calendar(self._selected_date.year, self._selected_date.month) # reconstruct calendar
Updated calendar to show the previous day.
recipes/Python/580725_Tkinter_Datepicker_like_jQuery_UI/recipe-580725.py