The router syncs its time from the Internet. So make sure that the router can connect to the Internet (NTP servers) after setting the corrent time zone.
The warning you are getting is a javascript (JS) check locally in the browser. If you use Brave browser, it has some security settings that prevent the JS from getting the computer's timezone. Use any other browser and see if the warning is gone.
Hi, forgot to mention I used Brave, Chrome (default settings) on PC and Safari (default settings) on my Macbook. Same result, I can use internet with the Beryl as repeater but can't sync time correctly like I said.