Right-click your Clock in the strip at bottom right of Windows - "adjust date/time" - or find the date & time settings control panel. In WIndows 10 it's probably a tile.

You should see "Change time zone..." button in the Date and Time settings, which leads to another screen with a drop-down menu of numbers and countries.

Americans and anyone set to USA time are put on Solhelm server. To get on Solhelm, change your time zone to (UTC-06:00) Central Time (US and Canada) then launch the game and Comrades.

European time zone locations will get you to Eos server. Tell Windows you're in London or (UTC+00:00) Casablanca ;)

New Zealanders, Asians and people far East are sent to Accordo. To join them take a trip to (UTC+9:30) Darwin.

Exit XV completely before changing timezone - going back to the Comrades title page is not enough.

Changing server conveys zero gameplay advantage, it just lets you play with your friends in another country who have the Final Fantasy XV: Steam Edition with Comrades DLC.

It is unintended user behaviour that can introduce more lag and jankiness to Comrades, such as players teleporting. In worst case, you might fall through the floor or not be able to see the boss! Good luck, Kupo.

https://steamhost.cn/steamcommunity_com/groups/ffxvcomrades has a group chat for starting missions at the same time and for meeting new friends to play with on all 3 servers.