An  Accurate  Clock

Well, nearly.  The US government set up a website some time ago that displays a real-time clock that is linked to an extremely accurate atomic clock.  The time displayed is accurate within limitations stated on that site - there is a slight error in the display owing to the small amount of time it takes for information to be sent over the Internet.  It also includes a nifty World map that shows which areas are in daylight and which are in darkness.  It now defaults to display Universal Time - much better than just US time zones - but it also defaults that that archaic US phenomenon, a 12-hour clock.  Fortunately, they've now introduced buttons that will change it to other timezones and/or display in 24-hour format.
(Though note: it only goes in 1 hour intervals - sorry, India!)

Meanwhile, I have found a far more useful site ( that will display a similarly accurate clock with a wide choice of presentations.  It will work in all time zones and can display in a variety of languages, plus it can be embedded as an IFRAME in any web page (see above).  More information here.