How to Set and Calibrate a Watch Using Atomic Time
30 September 2026 · 4 min read
Learn how to set your watch to the exact second and measure its daily drift, using an atomic-referenced clock and a simple week-long log.
Read the guidePlain-English guides on how time is measured, why watches drift, and how the world's time zones came to be.
Learn how to set your watch to the exact second and measure its daily drift, using an atomic-referenced clock and a simple week-long log.
Read the guideHow atomic clocks work, how UTC is built from hundreds of them, why leap seconds exist, and how that time reaches your phone and watch.
Read the guideThe real causes of watch drift in quartz and mechanical watches: temperature, magnetism, position, wear and age, and when to service yours.
Read the guideFrom local solar noon to railway time, the 1884 Greenwich meridian and daylight saving: how time zones came about, and why some are so odd.
Read the guideUTC, TAI, GPS time, Unix time and your device clock all count seconds differently. Here is how they relate and which one you should trust.
Read the guide