Subject: date -Ins has a comma!!

From: aaa jjj <[email-masked]>
Date: Thu, 27 Apr 2023 16:53:53 +0200

Hi,

is it not a bug, that if I do

LC_ALL=C date -u -Ins

gives me this:
2023-04-27T13:30:15,976772648+00:00

I'm talking about the comma. What is it doing there???
Should this not be a dot instead?

Here's the code:
https://github.com/coreutils/coreutils/blob/35adc746a000ac1f8d1d817a6a3a60d5b80daef5/src/date.c#L465

What does ISO 8601 say about this?

Look at other languages:

node -e 'console.log(new Date().toISOString())'
-> 2023-04-27T13:40:58.846Z

python3 -c 'from datetime import datetime;
print(datetime.now().isoformat())'
-> 2023-04-27T16:23:40.217313

python3 -c 'from datetime import datetime, timezone;
print(datetime.now(timezone.utc).isoformat())'
-> 2023-04-27T14:23:40.228151+00:00

python3 -c 'from datetime import datetime, timezone;
print(datetime.now(timezone.utc).astimezone().isoformat())'
-> 2023-04-27T16:23:40.238908+02:00

PS:
Hell, you cannot simply change it now (backwards-compatibility), but what
about another option flag or whatever...

Thanks.
A