javascript-clock
This utilizes the requestAnimationFrame with polyfil
http://paulirish.com/2011/requestanimationframe-for-smart-animating/
http://my.opera.com/emoller/blog/2011/12/20/requestanimationframe-for-smart-er-animating
requestAnimationFrame polyfill by Erik Möller. fixes from Paul Irish and Tino Zijdel MIT license
Check out Demo