Detecting changes to system time in JavaScript

Question

How can I write a script to detect when a user changes their system time in JS?

Answer 1

var last_time = new Date().getTime();
setInterval(function() {
    var time = new Date().getTime();
    var offset = time - last_time;
    if(offset < 0 || offset > 1500) {
        // Time has been changed
    }
    last_time = time;
}, 1000);

In theory, this should work. It will check every second to make sure the time hasn't been changed. Note that I use 1100 milliseconds as most JS interpreters don't fire off events at exactly the time specified.

Hope this helps!