@jlrdw Thanks for the input, but neither of these address the problem, which is one of display
The Carbon issue is related to just setting the timezone and then outputs the format in a specific format, not user timezone dependent formatting.
eg
echo now()
->tz('America/Chicago')
->toDayDateTimeString();
echo now()
->tz('Europe/London')
->toDayDateTimeString();
echo now()
->tz('Europe/Berlin')
->toDayDateTimeString();
echo now()
->tz('Asia/Tokyo')
->toDayDateTimeString();
outputs
Fri, Mar 19, 2021 2:55 PM
Fri, Mar 19, 2021 7:55 PM
Fri, Mar 19, 2021 8:55 PM
Sat, Mar 20, 2021 4:55 AM
So, it works in that it writes the date out in an unambiguous format, but its not as per my requirements.