'Return the label for time *x* at position *pos*'

def __call__(self, x, pos=0):

    ind = int(np.round(x))
    if ((ind >= len(self.t)) or (ind <= 0)):
        return u''
    dt = num2date(self.t[ind], self.tz)
    return cbook.unicode_safe(dt.strftime(self.fmt))
