Document time.ctime format

[RogerCaldwell]

BPO	13927
Nosy	@birkenfeld, @abalkin, @vstinner, @ericvsmith, @bitdancer, @ztane, @harmands, @pganssle, @csabella, @miss-islington
PRs	bpo-13927: time.ctime and time.asctime return string explantion #11303 [3.8] bpo-13927: time.ctime and time.asctime return string explantion (GH-11303) #16022
Files	ctime-doc.patch: patch file

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2019-09-12.10:35:48.238>
created_at = <Date 2012-02-02.20:49:35.904>
labels = ['3.8', 'type-feature', '3.7', 'docs']
title = 'Document time.ctime format'
updated_at = <Date 2019-09-12.10:35:48.237>
user = 'https://bugs.python.org/RogerCaldwell'

bugs.python.org fields:

activity = <Date 2019-09-12.10:35:48.237>
actor = 'p-ganssle'
assignee = 'docs@python'
closed = True
closed_date = <Date 2019-09-12.10:35:48.238>
closer = 'p-ganssle'
components = ['Documentation']
creation = <Date 2012-02-02.20:49:35.904>
creator = 'Roger.Caldwell'
dependencies = []
files = ['45073']
hgrepos = []
issue_num = 13927
keywords = ['patch']
message_count = 16.0
messages = ['152475', '152483', '152496', '153310', '153311', '278557', '332336', '332422', '332584', '339973', '339975', '339980', '340207', '352091', '352095', '352098']
nosy_count = 11.0
nosy_names = ['georg.brandl', 'belopolsky', 'vstinner', 'eric.smith', 'r.david.murray', 'Roger.Caldwell', 'ztane', 'harman786', 'p-ganssle', 'cheryl.sabella', 'miss-islington']
pr_nums = ['11303', '16022']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue13927'
versions = ['Python 2.7', 'Python 3.7', 'Python 3.8']

[RogerCaldwell]

Hi. I found this today and thought I would report. I could not find anywhere that it was expected behavior. When using time.ctime() to convert a date which only has 1 digit in the day position it returs a string with 2 spaces after the month vs one.

example
In [2]: import os,time

In [3]: time.ctime(os.path.getmtime('file.cfg'))
Out[3]: 'Tue Dec 13 18:52:58 2011'

In [4]: time.ctime(os.path.getmtime('14d-1.log'))
Out[4]: 'Tue Feb 1 19:53:11 2011'

Is this expected behavior?

[ericvsmith]

That's definitely the expected behavior. It's the same as the C library version of ctime().

But I couldn't find it documented in the Python docs, so I'm changing this to a documentation issue.

Thanks for the report.

[birkenfeld]

asctime() docs say it's a 24 char string.

[vstinner]

asctime() docs say it's a 24 char string.

I'm not sure that all platform conform to this "specification"... which is not future proof!

$ ./python 
Python 3.3.0a0 (default:af1a9508f7fa, Feb 14 2012, 01:18:15) 
[GCC 4.6.2 20111027 (Red Hat 4.6.2-1)] on linux
>>> import time
>>> time.ctime(2**38)
'Wed Jul 14 08:09:04 10680'
>>> len(time.ctime(2**38))
25

I suppose that you can say that the month day is formatted as 2 characters (padded with a space if needed).

[bitdancer]

Or you could give the strftime specification string that produces the equivalent output.

[harmands]

I was bored, I generated a patch for this.

Hope this helps :)

[ztane]

This should be added to asctime too.

The space-padded behaviour complies with the C standard which was the intent - after all, before it was using C asctime directly, and says that unlike C asctime, it doesn't have the newline character, meaning that as a rule, it should then behave similar to it, and only exception is marked.

Unfortunately MSVC asctime has been incorrectly using leading zeros (https://stackoverflow.com/q/53894148/918959).

[harmands]

I have created the PR as mentioned, I have added the example for time.ctime() and also added the note to time.asctime.

[harmands]

I have created a PR for the patch that I submitted, as this is my first contribution to the docs, I need to know that how do we decide if a change has to make an entry to [Misc/NEWS.d/next/](https://github.com/python/cpython/blob/main/Misc/NEWS.d/next) or needs skip news tag?