Modify file create / access / write timestamp with python under windows

Question

I tried to find an easy way to modifiy a file timestamp under windows using python, but there was not much clear information on the web. After searching a while I got a solution. To shorten the search for others, the code follows here.

It might be done easier and more beautiful, but it works. The only thing I didn't solve is the summer time - winter time issue, i.e. if a time in summer is given, the result differs by one hour. Maybe someone can add a correction?

from win32file import CreateFile, SetFileTime, GetFileTime, CloseHandle 
from win32file import GENERIC_READ, GENERIC_WRITE, OPEN_EXISTING
from pywintypes import Time
import time

import sys
import os

if len(sys.argv)<5:
  pfile = os.path.basename(sys.argv[0])
  print "USAGE:\n\t%s <createTime> <modifyTime> <accessTime> <FileName>\n" % pfile
  print "EXAMPLE:"
  print '%s "01.01.2000 00:00:00" "01.01.2000 00:00:00" "01.01.2000 00:00:00" file' % (pfile) 
  sys.exit()  

# get arguments  
cTime = sys.argv[1] # create
mTime = sys.argv[2] # modify
aTime = sys.argv[3] # access
fName = sys.argv[4]

# specify time format
format = "%d.%m.%Y %H:%M:%S"
offset = 0 # in seconds

# create struct_time object
cTime_t = time.localtime(time.mktime(time.strptime(cTime,format))+offset)
mTime_t = time.localtime(time.mktime(time.strptime(mTime,format))+offset)
aTime_t = time.localtime(time.mktime(time.strptime(aTime,format))+offset)

# visually check if conversion was ok
print
print "FileName: %s" % fName
print "Create  : %s --> %s OK" % (cTime,time.strftime(format,cTime_t))
print "Modify  : %s --> %s OK" % (mTime,time.strftime(format,mTime_t))
print "Access  : %s --> %s OK" % (aTime,time.strftime(format,aTime_t))
print

# change timestamp of file
fh = CreateFile(fName, GENERIC_READ | GENERIC_WRITE, 0, None, OPEN_EXISTING, 0, 0) 
createTime, accessTime, modifyTime = GetFileTime(fh) 
print "Change Create from",createTime,"to %s" % (time.strftime(format,cTime_t))
print "Change Modify from",modifyTime,"to %s" % (time.strftime(format,mTime_t))
print "Change Access from",accessTime,"to %s" % (time.strftime(format,aTime_t))
print

createTime = Time(time.mktime(cTime_t))
accessTime   = Time(time.mktime(aTime_t))
modifyTime    = Time(time.mktime(mTime_t))
SetFileTime(fh, createTime, accessTime, modifyTime) 
CloseHandle(fh)

# check if all was ok
ctime = time.strftime(format,time.localtime(os.path.getctime(fName)))
mtime = time.strftime(format,time.localtime(os.path.getmtime(fName)))
atime = time.strftime(format,time.localtime(os.path.getatime(fName)))

print "CHECK MODIFICATION:"
print "FileName: %s" % fName
print "Create  : %s" % (ctime)
print "Modify  : %s" % (mtime)
print "Access  : %s" % (atime)

Answer 1

There are two places where you might want to correct for winter/summer difference of one hour. In both cases, we make use of the tm_isdst field, which time.localtime conveniently calculates to tell us whether Daylight Savings Time (DST) was in effect for a particular timestamp.

Input Correction

If you are setting a winter timestamp during summer, or vice versa, it will become off by an hour when its matching season comes around unless you compensate before calling SetFileTime:

now = time.localtime()
createTime = Time(time.mktime(cTime_t) + 3600 * (now.tm_isdst - cTime_t.tm_isdst))
accessTime = Time(time.mktime(aTime_t) + 3600 * (now.tm_isdst - aTime_t.tm_isdst))
modifyTime = Time(time.mktime(mTime_t) + 3600 * (now.tm_isdst - mTime_t.tm_isdst))
SetFileTime(fh, createTime, accessTime, modifyTime) 

Output Correction

To make Python reports match Windows Explorer, we apply the correction before calling strftime:

# check if all was ok
now = time.localtime()
ctime = os.path.getctime(fName)
mtime = os.path.getmtime(fName)
atime = os.path.getatime(fName)
ctime += 3600 * (now.tm_isdst - time.localtime(ctime).tm_isdst)
mtime += 3600 * (now.tm_isdst - time.localtime(mtime).tm_isdst)
atime += 3600 * (now.tm_isdst - time.localtime(atime).tm_isdst)
ctime = time.strftime(format,time.localtime(ctime))
mtime = time.strftime(format,time.localtime(mtime))
atime = time.strftime(format,time.localtime(atime))

Both Corrections

Beware, if you apply both, your Python output will again seem to mismatch your input. This may be desirable (see below), but if it bothers you:

• Choose only Input Correction if you prefer timestamps that look right at their native time of year.
• Choose only Output Correction if you're used to seeing them jump an hour twice a year as DST takes effect and then goes away.

---

Why is DST so inconsistent?

Python and Windows have chosen different methods to convert timestamps between UTC and the local time zone:

• Python uses the DST code that was in effect at the timestamp. This way, the time stamp has a consistent representation year-round.

• Windows uses the DST code in effect right now. This way, all time stamps shown have the same implicit code.

This is evident if you use '%Z' to include the time zone in the converted string (PST vs. PDT, for example) but since most apps (including Windows Explorer) do not, an apparent one-hour inconsistency can manifest.

Example

When printed with explicit time codes, it becomes clear that the stamps in each column really do all represent the same instant in time:

File #1 (January)        File #2 (June)
2000-01-30 20:00:00 UTC  2000-06-22 20:00:00 UTC

observed in January in California:
2000-01-30 12:00:00 PST  2000-06-30 13:00:00 PDT  [Python]
2000-01-30 12:00:00 PST  2000-06-30 12:00:00 PST  [Windows]

observed in June in California:
2000-01-30 12:00:00 PST  2000-06-30 13:00:00 PDT  [Python]
2000-01-30 13:00:00 PDT  2000-06-30 13:00:00 PDT  [Windows]

observed in June in New York:
2000-01-30 15:00:00 EST  2000-06-30 16:00:00 EDT  [Python]
2000-01-30 16:00:00 EDT  2000-06-30 16:00:00 EDT  [Windows]

It would be nice if we could ask strftime to honor the tm_isdst field, to match Windows Explorer and most other apps that display file timestamps, but at least there's a simple workaround to do the calculation ourselves.

def adjustForDST (seconds):
    now = time.localtime()
    correction = 60*60 * (now.tm_isdst - time.localtime(seconds).tm_isdst)
    return seconds + correction

time.strftime(format, time.localtime(adjustforDST(mtime)))

Sources:

http://bytes.com/topic/python/answers/655606-python-2-5-1-broken-os-stat-module http://search.cpan.org/~shay/Win32-UTCFileTime-1.58/lib/Win32/UTCFileTime.pm

If the cpan link breaks again with a new revision, find it this way:

https://www.google.com/search?q=UTCFileTime.pm

Answer 2

Using os.utime, you can change the atime, mtime (no ctime).

>>> import time
>>> import os
>>> t = time.mktime(time.strptime('16.01.2014 00:00:00', '%d.%m.%Y %H:%M:%S'))
>>> t
1389798000.0
>>> os.utime('..\path\to\file', (t,t)) # <---
>>> os.path.getmtime('..\path\to\file')
1389798000.0