How does the online clock work?
This clock reads the time directly from your own device and redraws it every frame. There is no server call and no network request after the page loads, which is why it stays accurate even if your connection drops. The analog dial and the digital readout are driven by the same tick, so they never disagree: the hour hand creeps forward continuously rather than jumping at the top of each hour, exactly as a mechanical clock does.
Because everything runs locally, the clock is only ever as accurate as the device it runs on. Modern phones and computers synchronise themselves against internet time servers using NTP (Network Time Protocol), which typically keeps them within a few milliseconds of the atomic reference clocks maintained by national standards bodies. If your system clock has drifted, the page will faithfully show the wrong time — the fix is in your operating system, not in the browser.
Reading an analog clock
Analog dials are still worth knowing, and they are still what most classrooms teach with. The three hands work at very different speeds:
- Hour hand — the short, thick one. It travels once around the dial every twelve hours, so it moves roughly 30° per hour.
- Minute hand — the long one. One full revolution per hour, 6° per minute.
- Second hand — the thin one, one revolution per minute.
A common stumbling block is that the hour hand is between numbers for most of the hour. At half past four, the hour hand sits midway between the 4 and the 5 — it reads "4", not "5", because the hour has not finished yet. Reading the minute hand first and the hour hand second avoids the mistake.
12-hour and 24-hour formats
Use the 12h / 24h buttons above to switch between formats; your choice is remembered on this device. The 12-hour clock splits the day into two halves labelled AM (ante meridiem, before midday) and PM (post meridiem, after midday), and is the everyday standard in the United States, Canada, Australia and the United Kingdom. The 24-hour clock runs 00:00 through 23:59 without repeating and is the civil standard across most of Europe, Latin America and Asia, as well as the international convention in aviation, medicine, the military and computing — precisely because it cannot be misread.
Two edge cases catch people out in 12-hour notation: midnight is 12:00 AM and midday is 12:00 PM, which feels backwards to almost everyone. Timetables often sidestep the ambiguity entirely by writing 11:59 PM or 12:01 AM instead. In 24-hour notation the same instants are simply 00:00 and 12:00, with no ambiguity to resolve.
Using the clock as a display
Press F11 (or Ctrl+Cmd+F on a Mac) to go full screen and the clock becomes a standalone display. That makes it useful for:
- A classroom or lecture-hall clock projected on the board.
- A second monitor or an old tablet repurposed as a desk clock.
- An on-screen clock for streams and video calls, where viewers need a visible reference.
- Reception areas, workshops and kitchens where a phone would be in the way.
The dark theme is the default and is a deliberate choice for always-on displays: it draws less power on OLED panels and is far easier on the eyes in a dim room. Use the moon button in the header to switch to the light theme if you prefer.
Frequently Asked Questions
Why does the clock show the same time as my device?
Because it reads your device's own clock rather than a remote server. If the time is wrong, turn on automatic date & time in your system settings — on Windows under Settings → Time & language, on macOS under System Settings → General → Date & Time, and on Android or iOS under the Date & Time menu.
How accurate is it?
It is exactly as accurate as your operating system's clock, which on any modern device with automatic time enabled is normally within a fraction of a second of official time. The page itself adds no meaningful delay.
Does it work offline?
Yes. Once you have opened the page it is cached by a service worker, so it keeps working without a connection. You can also install it as an app from your browser menu.
Will my screen turn off while the clock is showing?
That depends on your device's power settings, which a web page cannot override. For a permanently visible clock, extend or disable the screen timeout in your system settings.
Can I show the time in another city?
Yes — use the world clock to track several cities at once, or open a dedicated page such as New York, London or Tokyo.
Related tools
Need to measure time rather than read it? Use the stopwatch for elapsed time with laps, the timer to count down to zero, the alarm to be woken at a set time, or the time calculator to add and subtract durations.