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:

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