In reverse order of accuracy, here are the three most precise ways of setting a watch.
- Convene a meeting of your homeowners association or city council to obtain permission to erect a 78-foot dipole antenna in your neighborhood or yard or on the roof of any local municipal building. Being sure to ground the antenna properly, attach it to a shortwave radio receiver. Tune to 5,000, 10,000 or 15,000 kilohertz and listen for a clicking sound. When it reaches ten seconds before any minute, a voice will come on and announce the time. Set your watch to the chime signal. Allowing for errors owing to the speed of light, atmospherics and system delays, your setting will be precise enough for the purposes of celestial navigation with a sextant.
- Every modern computer or cellphone has a clock function. System settings on these can result in a minor lag of a few seconds, but if you set it to one of these, your watch will be acceptably accurate.
- Contact Hammacher & Schlemmer and have them send you their finest remote atomic clock signal reception wristwatch. Using the average output from a bank of ten government cesium clocks, calculate the number of quadrillionths of a second of lag time there is in the mechanism. Calibrate for the error, and you will have the second most reliable timekeeping in the world.
- If you require something more exact than that, wait until about 8:25 or so. Prepare your watch for synchronization at 8:30 PM. Keep your finger on the winding crown, ready to press it in on cue. You're going to have to be on your toes. Now, watch Roo sleep. Examine every movement she makes carefully. A few seconds prior to 8:30, her eyes will open. She will then raise her head and fix you with a look wondering where her evening cookies are. At that instant, press the crown of your watch in. It will be exactly 8:30. This is the method the Jet Propulsion Laboratory uses with radiotelescope arrays to triangulate the position of galaxies at the edge of the universe, because it never fails.