Renommage date fichiers

import os, glob
from datetime import datetime, timedelta

ext = '.jpg'
# ext = '.nef'
fmt = '%Y-%m-%d %H.%M.%S'+ext  # renommer d'abord les fichiers '2018-05-17 22.42.42-1' et '2018-05-17 22.42.42-2'

imgs = glob.glob('*'+ext)

for file in imgs:
    timestamp = datetime.strptime(file,fmt)
    delta = timedelta(hours=9)
    os.rename(datetime.strftime(timestamp,fmt),datetime.strftime(timestamp-delta,fmt))