Looking at doing 'New York, 'London' & 'Tokyo' traditional round clocks (basic black outlines) should these really be done with javascript? ( and not to be too picky, but it would be great if it was compatible with nearly all browsers/the latest )

Is there anything proprietary about this?

Can real time updates be done with javascript -- also, what if I am not linked to an external site?

I have noticed the graphic portion being done with a "canvas" tag that I am unfamilair with (html5)

- Much much appreciate thoughts on this.