'Find all folds with the same value of isdst on both sides of the transition.'

def nondst_folds(self):

    for ((_, prev_ti), (t, ti)) in pairs(zip(self.ut, self.ti)):
        shift = (ti[0] - prev_ti[0])
        if ((shift < ZERO) and (ti[1] == prev_ti[1])):
            (yield (datetime.utcfromtimestamp(t), (- shift), prev_ti[2], ti[2]))
