UTC is a timezone, though. Or am I misunderstanding what you're saying?
But the title specifically say "from a UTC string", so it _is_ a UTC string, always.
> ascii string you are showing us to actually make sense in our specific locale
Locale and TZ are two completely separate things. You can use any locale in any TZ. You can use any locale in any location, too.
Without any marking, it could be anything
Noon UTC is "12:00Z".
RFC 3339 is nice for this reason. Always UTC and terminated with a Z.