Pre-owned men’s Rolex Datejust in stainless steel with a blue dial and roman numeral markers.

There are thousands of types of watches in the world and many of them proudly display the word “chronometer” on their dials. But what is a chronometer, really? Let’s break it down:

Chronos = the Greek word for “time”
Metron = the Greek word for “measure”

chronos + metron = chronometer, or an instrument that measures time

A chronometer is simply an extremely accurate watch or clock.  A Swiss chronometer is a watch, usually mechanical, that has gone through testing and has been verified by the official Swiss watch testing bureau, the Swiss Official Chronometer Control (COSC). The test, conducted for 15 days and nights, checks the movement’s accuracy in five different positions and at various temperatures that simulate conditions under which the watch will be worn. The COSC issues ratings certificates to the watches that pass, and these serve as proof of superior quality.

Here’s one last tidbit: although “chronometer” and “chronograph” sound similar, they are not the same. While a chronometer is an accurate timekeeper, a chronograph is a watch with a stopwatch function.