How it works is that the server spits out a GMT timestamp and the javascript (using your browser's timezone offset and current time) turns it into a relative "3 hours ago", "1 min ago", etc.

I can't do anything if your system time isn't accurate. Though I think it'd be a nice customization option for users to be able to toggle between relative timestamps ("3 hours ago") and absolute timestamps shifted into your timezone "1/2/2015 3:02pm".