Python: move files to creation date named directories

move.py

#!/usr/local/bin/python3
import os, time, shutil, sys
dir = sys.argv[1]
os.chdir(dir)
for f in os.listdir('.'):
    ftime = time.gmtime(os.path.getmtime(f))
    year = str(ftime.tm_year)
    mon = str(ftime.tm_mon)
    day = str(ftime.tm_mday)
    if len(mon) == 1: mon = "0" + mon
    if len(day) == 1: day = "0" + day
    ctime_dir = year + mon + day
    if not os.path.isdir(ctime_dir):
        os.mkdir(ctime_dir)
    dst = ctime_dir + "/" + f
    shutil.move(f, dst);
    print("File " + f + "has been moved to " + dst)