Hi @Otto Medin !
HTTP is basically US ASCII 7bit with some "handcrafted" extensions
- somehow "UTF 7.6" 
🤪 focussing on octets
it works for äöü  but NOT for €  (x20AC)  >>> in URL  %u20AC

for details: https://softwareengineering.stackexchange.com/questions/304419/what-encoding-are-the-http-status-and-header-lines

my hint: Try to avoid it in HTTP headers and stick with 7bit ASCII to be on the save side
browsers are less risk for problems but old applications are

Manipulating time values is a risky ground. See this simple example.
 

USER>write ?1%, $ZTZ," : ",$zdt($ZTS)," : ",$zdt($now())," : ",$zdt($h)
               -60 : 07/04/2024 16:03:42 : 07/04/2024 17:03:42 : 07/04/2024 18:03:42
  • $ZTZ  is the geographic offset to UTC in minutes
  • $ZTS is UTC time  (no daylight saving !)
  • $NOW() is UTC adjusted by $ZTZ   (no daylight saving  or special time zone adjustment)
  • $H is based on the time set in your server OS  

So for international applications using anything else than UTC is an open trap you might be caught in.

This was the original motivation to use UTC in ENSEMBLE and it's descendants and followers