Accurate Macintosh Clock

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There used to be an app that split your local timezone up into km's worked out your location then gave you your true time but I can't remember what it was called.

 

Why in the world would you want micro-second accuracy? It would be entirely useless, even from a scientific standpoint.

I don't think there is a display in the world that has mega-hertz refresh rates. The best LCD TV's out there, refresh at 120Hz. Even Plasma's don't refresh more than 600Hz. Your brain wouldn't even be able to interpret numbers moving that quickly.

So, you can make your own micro-second clock. Just use a standard clock, and instead of actually telling time for the digits after a thousandth of a second, just have a slightly morphing blur graphic. The net effect would be the same. If you wanted, you could even "pause it" and display random numbers in place of the blur, the accuracy of which would be arbitrary.

 

What do you mean by true time? Do you mean local time as opposed to standard time and daylight savings time?

To the OP's question, Internet time servers, which your computer hopefully uses to set its clock continuously, use the NTP (Network Time Protocol) for clock synchronization. Over the Internet, this protocol is accurate to within tens of milliseconds--a full order of magnitude less accurate than you want. NTP is accurate to 1 millisecond over a LAN, but the LAN gets its time from the Internet.

To do better, you need a GPS clock. GPS time is accurate to ±340 nanoseconds. To achieve this accuracy, however, you will need to assemble your system while taking everything into account. In the sub-microsecond regime, your cabling will have a profound affect on your computer clock's accuracy.