I have a GL.iNet Beryl (GL-MT1300) and the Time Zone is set to America. But when I go on vacation to Asia, I use it as Repeater or Cable, my apps show the Time Zone for Asia, although it is set to America in the GL router page.
Why is this and is it possible to show it as America Time Zone or do I have to setup VPN?
Your apps will decide on whatever they are looking for. Might be GPS. Might be next server, etc. etc
Setting the time zone on the router will ONLY set it on the router.
The timezone is not part of the NTP (Network Time Protocol) - although there is a time syncronization service available on your router (and there are also many robust internet NTP servers), it only syncronizes the UTC date/time and its up to individual devices to both know and adjust UTC to the local timezone.
Portable devices with built-in GPS (like cell phones and many tablets) use their geo-location to determine the local timezone. Other devices (like a Roku streaming stick) use the IP address to try and determine the local timezone (and sometimes fair miserably). Some laptop/desktop operating systems can also use the IP address to determine their local timezone (again, sometimes failing miserably), but usually this feature is opt-in and must be enabled in settings; for the most part, the timezone is manually set when you install the operating system and must be manually changed for other timezones.
So… with the current state of the tech world… this isn’t a router problem. Its your local machine’s problem. So, if (for example) your laptop is displaying the date/time for the wrong timezone, see if your laptop’s timezone settings include an optional “automatic” setting (which would use your IP address)… otherwise, change it manually.