Untitled

Javascript event triggers based on local clock
// get current time in msecs to nearest 30 seconds
var msecs = new Date().getTime() % 30000;

// wait until the timeout
setTimeout(callback, 30000 - msecs);

function redraw() {
    var interval = 30000;

    // work out current frame number
    var now = new Date().getTime();
    var frame = Math.floor(now / interval) % 2; // 0 or 1

    // do your stuff here
    .. some time passes

    // retrigger
    now = new Date().getTime();
    setTimeout(redraw, interval - (now % interval));
}

redraw();

var t=setInterval("check()",1000);
function check(){
    var d = new Date();
    if(d.getSeconds()  == 0)
    {
        alert('do something');
    } else if (d.getSeconds() == 30)
    {
        alert('do something else');
    }
}