If by 'handles' you mean hands, what I built does that with CSS3's animation and transformations. No JS necessary. It's setting the initial positions that's the problem - CSS has no clock functionality.
The only non-JS solution is to tell people to only load the page at exactly 12:00:00, but that's a bit impractical.
That's actually a lazy-developer-only-bothered-with-the-webkit-animation-class issue rather than a Firefox issue. Adding keyframes, moz-keyframes, and o-keyframes would make it cross-browser.