It is a read-only variable.
Here is a simple, useless example.
PHP Code:
function onCreated() {
// set a variable to whatever timevar2 is currently
this.oldtime = timevar2;
setTimer(5);
}
function onTimeout() {
// output the difference between the current time, and the old time to know how many seconds have passed
echo(timevar2 - this.oldtime SPC "seconds passed");
}