Exact time
--:--:--.0
Checking the time against our server…
1. Tap when your watch reaches the minute
- Watch your watch’s seconds, not this screen.
- The moment the second hand reaches 12, or the display flips to :00, tap the big button (or press the space bar).
- Do it three times, a minute apart, then save the reading.
No taps yet.
This works while your watch is within 30 seconds of the right time. If it’s further out, set it close first, then start your readings.
2. Your readings
No readings saved for this watch yet.
| When | Your watch was | After | Delete |
|---|
3. How accurate is it?
🔒 Your readings stay in this browser. The only thing we fetch is the time from our own server.
How it works
The big clock is set from our server, which keeps exact time, and we allow for any difference in your device’s own clock. When you tap, we note where the exact seconds are. If your watch reached :00 when the exact time was 58.3 seconds past, your watch is 1.7 seconds fast.
One reading only tells you how far out the watch is now, which depends on when you last set it. The useful number is the rate: how much that changes a day. Save a reading today and another tomorrow without touching the watch, and the difference is the rate. Readings a week apart give a sharper answer, because your tap is never perfect and the error gets spread over more days.
What’s normal?
| Kind of watch | Typical accuracy |
|---|---|
| Quartz (battery) | Many are rated to about ±15 seconds a month: half a second a day |
| Chronometer-certified mechanical | −4 to +6 seconds a day (the COSC test) |
| Other automatic or hand-wound | Often quoted at around ±10 to ±20 seconds a day, varying with position, temperature and how wound it is |
| Smartwatch, GPS or Bluetooth watch | Set automatically, so this test isn’t much use |
Our lesson Quartz, automatic or solar? explains why, and what to do about a watch that has suddenly started gaining minutes a day.