Make a more accurate clock

How can I make the clock in my Mac as accurate as my GPS clock?

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The internal clock in a Mac is designed to deliver high-resolution time for essential services such as the file system, and to provide reasonably accurate clock time corrected using a range of references, including Apple's internet time service. The latter isn't as accurate as you'll get from a GPS clock, and even in Apple's devices with built-in GPS receivers, their time signals aren't used to improve clock accuracy.