read csv, format date, sort by date, add header, write to file, without pandas

no_pandas.py

with open('test.csv', mode='r+', newline='') as f:
    data = list(csv.reader(f))
    for i, v in enumerate(data):
        v[0] = datetime.strptime(v[0], "%d-%b-%y").date().strftime('%Y-%m-%d')
        data[i] = v
    data = sorted(data, key=lambda row: datetime.strptime(row[0], '%Y-%m-%d'))
    writer = csv.writer(f)
    header = ['date', 1, 2, 3, 4, 5]
    f.seek(0)
    f.truncate()
    writer.writerow(header)
    writer.writerows(data)