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Sorry if my topic seems unclear but I'm coming from the world of IBM's main frame.
If I correctly understand, under Unix, ctime attribute of a file is not the creation date/time but the date/time of last change of an attribute, and if we modify a file, we modify its mtime, thus an attribute, thus its ctime also.
And IOS comes from the same kernel as Unix...
Thus my question is: is it possible to update/modify a file (in place) without modifying its ctime?

I'm not sure about when exactly the ctime is updated. There is an os.utime function that can be used to change the atime and mtime (but not the ctime), so you could use that to preserve the access/modification times.

Thanks for spending your time.
I know utime but I want to know if it's possible to keep the real creation time.

The question is for what you need this. If you want to preserve ctime value even when you modify file content / metadata, then there's no way. But if you want to know real time when the file was created, fstat64 & birthtime (not ctime) is your friend. Or NSFileCreationDate attribute on iOS 64-bit (NSFileManager.attributesOfItemAtPath:error:).

@zrzka I only want to know the creation date/time, thus this birthtime should be what I need, but I don't understand how to use it. Thanks for your help

Copy & paste this script to your Pythonista and run it.

from objc_util import ObjCClass
import editor

NSFileManager = ObjCClass('NSFileManager')
NSFileCreationDate = 'NSFileCreationDate'

attrs = NSFileManager.defaultManager().attributesOfItemAtPath_error_(ns(editor.get_path()), None)
creation_date = attrs[NSFileCreationDate]

print('File name: {}'.format(editor.get_path()))
print('File creation date: {}'.format(creation_date))
print('File creation timestamp: {}'.format(creation_date.timeIntervalSince1970()))

Console output

File name: /private/var/mobile/Containers/Shared/AppGroup/6644AB67-CC6B-4108-B96C-5DCDAC15FB7C/Pythonista3/Documents/birthtime.py
File creation date: 2017-08-11 14:55:52 +0000
File creation timestamp: 1502463352.8284547

@zrzka "ns not defined" error, but if I replace ns(...) by a file name, it's ok.
Thanks a lot for your help.

Ok, I also imported ns 😅

That's how Pythonista works. Always forgot to reset env before testing and some of these things are already imported. Glad you fixed it by yourself :)

Analyze (pyflakes) in the wrench menu can help you to see these issues.