@property
def datetime_nextpos(self):
    if ((self._datetime_nextpos is None) and (not self._datetime_calculated)):
        _ = self.datetime
    return self._datetime_nextpos
@property
def datetime_nextpos(self):
    if ((self._datetime_nextpos is None) and (not self._datetime_calculated)):
        _ = self.datetime
    return self._datetime_nextpos