Free tool
Is your device clock right?
A two-step code refused for no reason, a “your connection is not private” warning everywhere: often, the device clock is simply off. We compare it with the official time, to the tenth of a second.
Official time
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Your device
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Your browser asks our server (continuously synchronised with atomic clocks through the NTP network) for the time five times in a row and keeps the fastest measurement. Only the time travels; nothing is kept.
Why a few seconds matter
Up to about thirty seconds, nobody notices. Beyond that, things start failing, with error messages that never mention the clock.
01
Two-step codes refused
Authenticator codes (Google Authenticator, Microsoft Authenticator, 1Password…) change every 30 seconds and are computed from the clock.
A phone that is 45 seconds off produces codes the server considers expired.
02
Certificate errors
A security certificate is valid between two dates. If the device thinks it is another day, every site shows “Your connection is not private”.
Typical after a dead battery on an old computer.
03
Emails and files dated wrong
Your emails arrive at the wrong place in the recipient's inbox, shared documents look older or newer than they are.
Office networks (Active Directory) also refuse logins beyond 5 minutes.
How to fix it: turn on automatic time
The right fix is never to set the time by hand, but to let the device synchronise itself. Also turn on the automatic time zone if you travel.
- Windows 10 and 11Settings › Time & language › Date & time: turn on Set time automatically, then click Sync now.
- macOSSystem Settings › General › Date & Time: turn on Set time and date automatically.
- iPhone and iPadSettings › General › Date & Time: turn on Set Automatically. If it is greyed out, check Screen Time restrictions.
- AndroidSettings › System › Date & time: turn on Set time automatically. On Samsung: Settings › General management › Date and time › Automatic date and time.
Still off after that? The device may be on a network that blocks time synchronisation (some corporate or hotel networks): try again on another connection. On an old computer, a clock that drifts after each shutdown often means the motherboard battery is worn out.
Questions
How accurate is the measurement?
The time the request takes to travel is split in two, like the NTP protocol does. The margin shown (“± 0.03 s”, for example) is half the round trip of the best of the five measurements. On a normal connection, it is well under a tenth of a second.
My clock is off by exactly one hour
That is almost always a time zone problem: the time was set by hand in the wrong zone, or daylight saving time was not applied. Turn on the automatic time zone.
