def from_bucket(self, bucket, native=False):
    '''
    Calculate the timestamp given a bucket.
    '''
    # NOTE: this is due to a bug somewhere in strptime that does not process
    # the week number of '%Y%U' correctly. That bug could be very specific to
    # the combination of python and ubuntu that I was testing.
    bucket = str(bucket)
    if self._step == 'weekly':
      year, week = bucket[:4], bucket[4:]
      normal = datetime(year=int(year), month=1, day=1) + timedelta(weeks=int(week))
    else:
      normal = datetime.strptime(bucket, self.FORMATS[self._step])
    if native:
      return normal
    return long(time.mktime( normal.timetuple() ))
Calculate the timestamp given a bucket.