How accurate is my watch?

Setting Your Watch for Accuracy

So, if even cheap quartz watches are accurate to within less than a second per day, why was your watch so far off when you walked into that office for your appointment? The likely reason is that you either didn't set it to the correct time in the first place, or you've been wearing it nonstop for ages, and possibly subjected it repeatedly to humidity and temperature extremes that affected its operation. But you probably don't need to buy a new watch. Instead, it's easier just to check it every few months against a reliable reference, and reset it if necessary.

If you're in the U.S., check with the National Institute of Standards and Technology, which has two radio stations, one in Colorado and the other in Hawaii, that provide a continuous time signal. You can access the Colorado station by phone at (303) 449-7111 and the one in Hawaii at (808) 335-4363. The time provided by telephone is accurate to within 30 milliseconds, which is the maximum delay caused by cross-country telephone lines [source: NIST].

The official U.S. government time, which is based on NIST and the U.S. Naval Observatory in Washington, D.C., is available over the Internet at [source: NIST]. NIST also provides a free program that will synchronize your Windows computer with the government's official clock [source: NIST].

In other parts of the world, you can set your watch to the correct time by consulting, a promotional Web site offered by a software company that gets its data from the Royal Observatory at Greenwich in the UK.

By syncing up with these timekeeping bodies every so often, perhaps you'll never be late for an important appointment again.