Exact Time: Online Clock Accurate to the Second
The time shown is checked against our server, and the tool tells you how fast or slow your device is. Digital or analog, full screen, with the time in major cities around the world.
- Free
- Accurate to the second
- Full screen
- World clock
100% private — Everything is processed directly in your browser: your files, voice, and image are never sent to Chatzam's servers.
How to check the exact time
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Open the page
The clock appears right away, then syncs with the server time within a few seconds. A green dot confirms the check.
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Look at the offset
Below the clock, the tool tells you whether your phone or computer is fast, slow or on time, along with the accuracy of the measurement.
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Choose the display
Digital or analog, 24-hour or 12-hour format, with or without seconds. The full-screen button turns your device into a big clock.
More than just a clock
Verified time
The time is compared several times with our server's clock, right when the second ticks over: on a good connection, your device's offset is measured to within a hundredth of a second.
Full date
Day of the week, the date written out, your detected time zone and its offset from Coordinated Universal Time (UTC), daylight saving time included.
Big clock
Giant digits or an analog dial, full screen, with the screen kept awake on supported browsers: ideal in a classroom, a meeting or during an exam.
World clock
Add the cities you care about: local time, time difference from you, next or previous day. Your list is saved in your browser.
How is the exact time measured?
Your device sets its own clock, but not always accurately: a computer that hasn't synced in a long time, or whose automatic time setting is turned off, can drift by several seconds or even minutes. To check, the page queries our server several times. Each response contains the server time, rounded to the second. By sending requests exactly when the second is about to change, and accounting for the network travel time, the tool narrows down the estimate with each try. The result is shown with its real margin of error, which mainly depends on the speed of your connection: a few hundredths of a second on a good line, more on a weak mobile signal. The clock on screen is then corrected for that offset.
Daylight saving time and time zones
Most of the United States moves its clocks forward one hour on the second Sunday in March (at 2 a.m. it becomes 3 a.m.) and back one hour on the first Sunday in November (at 2 a.m. it becomes 1 a.m.): on November 1, 2026, then on March 14, 2027. Eastern Time is UTC−5 in winter and UTC−4 in summer, Central Time UTC−6/−5, Mountain Time UTC−7/−6 and Pacific Time UTC−8/−7. Hawaii (UTC−10) and most of Arizona (UTC−7) don't change their clocks. Time differences with other countries therefore shift during the year: between New York and London the gap is usually 5 hours, but only 4 hours for two to three weeks in March and about one week in late October and early November, because Europe doesn't change its clocks on the same dates as the US. The world clock takes all of this into account automatically.
A big full-screen clock
Set on a desk or projected onto a board, a computer or tablet becomes a clock you can read from across the room. In class, it helps students manage their time during a test; in a meeting or at a conference, it shows the time without anyone reaching for their phone. The analog dial, with its twelve numbers and minute marks, is also great for learning to tell time: compare it with the digital display just below. In full screen, the tool asks the browser to keep the screen on, where that's supported. On iPhone, where web pages can't go full screen, the clock is enlarged within the page; remember to turn off Auto-Lock.
Frequently Asked Questions
What time is it exactly?
The time shown on the clock above, synced with our server's clock. The accuracy of the measurement is shown just below: usually a few hundredths of a second.
Why is my device's time wrong?
Computer clocks drift slightly over time. If automatic time setting is turned off, or if the device hasn't synced in a long time, the difference can reach several seconds.
How do I fix the time on my computer?
On Windows: Settings, Time & language, Date & time, then turn on "Set time automatically" and click "Sync now". On Mac: System Settings, General, Date & Time, with automatic setting turned on.
Does the screen stay on in full screen?
Yes, on browsers that allow it (Chrome, Edge, recent Safari…): the tool prevents sleep mode as long as the clock is in full screen and the page stays in the foreground.
Is my time sent anywhere?
No. The page only asks our server for the time, without sending anything. Your settings and your list of cities stay in your browser.