'Turns an NMEA datestamp format into a C{datetime.date} object.
@raise ValueError: When the day or month value was invalid, e.g. 32nd
day, or 13th month, or 0th day or month.'

def _fixDatestamp(self):

    date = self.currentSentence.datestamp
    (day, month, year) = map(int, [date[0:2], date[2:4], date[4:6]])
    year += (self.yearThreshold - (self.yearThreshold % 100))
    if (year < self.yearThreshold):
        year += 100
    self._sentenceData['_date'] = datetime.date(year, month, day)
