"I started some years ago with the goal of building a clock that would be accurate to better than one second per year (so I would have the fun of adjusting it when a leap second occurred). This simple goal resulted in a most interesting journey into electronics, horology, astronomy, test equipment, quartz oscillators, rubidium and cesium atomic clocks, frequency counters and phase comparators, GPS, Loran C, GOES, and WWVB radio receivers. By now I've exceeded that goal by a factor of a million. The best clock in my collection (a Hydrogen Maser) is accurate to better than one microsecond per year."
Dedicated to precise Time and Frequency: LeapSecond.com