It seems kind of silly that they couldn't have the servers send their Unix timestamp every few packets so the client could confirm how it needs to modify local time to properly display server time. That's quite possibly one of the lowest-cost operations that they could do, and is really easy to code.

It appears that the clients are using the computer's timezone to modify the timestamp before rendering; if someone has their timezone set wrong, or they just have a weird datetime set in their system clock, it could throw the rendered time way off.