time.ctime() uses %3d instead of %.2d to format.

[WilliamChaseling]

BPO	34642
Nosy	@vadmium
Superseder	bpo-13927: Document time.ctime format

^{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 2018-09-12.03:47:50.294>
created_at = <Date 2018-09-12.03:01:23.093>
labels = ['3.7', 'invalid', 'type-bug', 'library']
title = 'time.ctime() uses %3d instead of %.2d to format.'
updated_at = <Date 2018-09-12.03:47:50.286>
user = 'https://bugs.python.org/WilliamChaseling'

bugs.python.org fields:

activity = <Date 2018-09-12.03:47:50.286>
actor = 'martin.panter'
assignee = 'none'
closed = True
closed_date = <Date 2018-09-12.03:47:50.294>
closer = 'martin.panter'
components = ['Library (Lib)']
creation = <Date 2018-09-12.03:01:23.093>
creator = 'William Chaseling'
dependencies = []
files = []
hgrepos = []
issue_num = 34642
keywords = []
message_count = 3.0
messages = ['325114', '325115', '325117']
nosy_count = 2.0
nosy_names = ['martin.panter', 'William Chaseling']
pr_nums = []
priority = 'normal'
resolution = 'not a bug'
stage = 'resolved'
status = 'closed'
superseder = '13927'
type = 'behavior'
url = 'https://bugs.python.org/issue34642'
versions = ['Python 3.7']

[WilliamChaseling]

time.ctime() returns _asctime from a C module.
_asctime returns a PyUnicode_FromFormat() result using "%s %s%3d %.2d:%.2d:%.2d %d" as the string formatter.

This works: 'Wed Sep 12 22:30:00 2018'
Except when day <10, because it uses %3d instead of %.2d
'Wed Sep 2 22:30:00 2018'

This seems like it might be intended behavior for some reason, but I don't see the reason.

[WilliamChaseling]

It's easy to get around using .replace(' ', ' '), but it's still a bit annoying.

[vadmium]

I think "ctime" and "asctime" are supposed to wrap or imitate the standard C functions: <https://port70.net/~nsz/c/c11/n1570.html#7.27.3.2\>, so I think this is intended behaviour. But see bpo-13927 about improving the documentation.

For a single-digit day of the month, there is supposed to be two spaces. Using "%.2d" would produce "Sep02" or "Sep 02", with a leading zero. On the other hand, changing the double space to a single space would produce "Sep 2", without a leading zero.