Online Clock
A free full-screen online clock with seconds — a big digital clock online showing your local time, date, and time zone — plus a world clock, alarm clock, stopwatch, and countdown timer in one page. No download, no sign-up; everything runs in your browser.
The clock follows your device's system time and updates every second, showing the current time with seconds. It answers “what time is it” at a glance. Use the buttons to switch 12/24-hour format, hide the seconds, or go full-screen for classrooms, exams, and presentations.
Add cities to build your own world clock online board and track multiple time zones at once. The board starts with New York, London, and Tokyo — the current time in London, New York, and Tokyo side by side. Offsets update live and daylight saving time is handled automatically.
Your board is saved in this browser. Each card shows the live local time, date, current UTC offset, and how far ahead or behind you it is. Need a plain UTC clock online reference? Add “UTC” from the list.
Use this tab as an online alarm clock: pick a time, add a label, and set it as a daily alarm online. The alarm list shows how long until each alarm rings.
This online stopwatch is timestamp-based: switching tabs cannot make it drift. Press Lap to record splits — the table shows the split vs the running total for every lap.
| Lap | Split | Total |
|---|
Use the presets or type a custom duration for an online countdown timer with alarm — an online timer for cooking, workouts, meetings, and focus sessions.
The remaining time also appears in the browser tab title, so you can watch it without switching tabs.
Time zones, explained
The Earth rotates 360° roughly every 24 hours, so each 15° of longitude equals about one hour of solar time. That is the whole idea behind time zones: the planet is divided into 24 main bands, each keeping a time offset from the global reference, UTC (Coordinated Universal Time). A label like UTC+7 means clocks there run 7 hours ahead of UTC — when it is 12:00 UTC, it is 19:00 local. UTC−5 means 5 hours behind.
Not every zone sits on a whole hour. India uses UTC+5:30, Nepal uses UTC+5:45, and Newfoundland uses UTC−3:30. These odd offsets are historical and perfectly normal — the world clock above renders them correctly.
Daylight saving time (DST) moves clocks forward by one hour during summer to stretch evening daylight. The US and Canada spring forward on the second Sunday of March and fall back on the first Sunday of November; most of Europe shifts on the last Sundays of March and October; parts of Australia and New Zealand observe DST during the southern-hemisphere summer (roughly October to April). Many regions near the equator — including Indonesia, Singapore, India, and Japan — never use DST at all. Browsers keep all of these rules in the built-in IANA time-zone database, which is why the world clock cards above switch offsets automatically without any action from you. Those seasonal switchover rules are the daylight saving time dates your browser applies behind the scenes.
Popular time zones reference (UTC offset table)
| City | Time zone | Standard offset | Daylight offset | Notes |
|---|---|---|---|---|
| Honolulu | Pacific/Honolulu | UTC−10 | — | No DST |
| Los Angeles | America/Los_Angeles | UTC−8 | UTC−7 | DST Mar–Nov |
| Denver | America/Denver | UTC−7 | UTC−6 | DST Mar–Nov |
| Chicago | America/Chicago | UTC−6 | UTC−5 | DST Mar–Nov |
| New York | America/New_York | UTC−5 | UTC−4 | DST Mar–Nov |
| São Paulo | America/Sao_Paulo | UTC−3 | — | No DST since 2019 |
| London | Europe/London | UTC+0 | UTC+1 | DST Mar–Oct |
| Berlin | Europe/Berlin | UTC+1 | UTC+2 | DST Mar–Oct |
| Moscow | Europe/Moscow | UTC+3 | — | Permanent UTC+3 |
| Dubai | Asia/Dubai | UTC+4 | — | No DST |
| Mumbai | Asia/Kolkata | UTC+5:30 | — | Half-hour zone |
| Bangkok | Asia/Bangkok | UTC+7 | — | No DST |
| Jakarta | Asia/Jakarta | UTC+7 | — | No DST |
| Singapore | Asia/Singapore | UTC+8 | — | No DST |
| Shanghai | Asia/Shanghai | UTC+8 | — | No DST |
| Tokyo | Asia/Tokyo | UTC+9 | — | No DST |
| Sydney | Australia/Sydney | UTC+10 | UTC+11 | DST Oct–Apr |
| Auckland | Pacific/Auckland | UTC+12 | UTC+13 | DST Sep–Apr |
How accurate is an online clock?
JavaScript in a browser cannot ask a time server directly the way your operating system does — it can only read the device's system clock. That is not as bad as it sounds: Windows, macOS, Android, and iOS all synchronize themselves over the internet using NTP (Network Time Protocol), typically holding the system clock within a few dozen milliseconds of true time on a decent connection.
What this means in practice:
- On a healthy device, the clock above is accurate to well within one second — plenty for alarms, meetings, classrooms, and exams.
- If your device clock is wrong, this page shows the same wrong time. Turn on “set time automatically” in your system settings and the problem disappears everywhere, not just here.
- If you need the exact time online for scheduling across zones, the world clock cards show each city's live local time together with its current UTC offset — no manual conversion needed.
- Tab switching cannot drift the stopwatch or timer. They record a timestamp when you press start and compute elapsed time from the system clock, instead of counting ticks — so a frozen background tab, a busy CPU, or a minimized window changes nothing.
- The seconds you see tick once per second, which is the honest resolution of this display. Sub-second precision would be theater: your screen refreshes in discrete frames and the OS clock itself is the limiting factor.
Worked examples
Example 1 — Set a 6:30 AM daily alarm
- Open the Alarm tab and set the time picker to 06:30.
- Type a label such as “Work” and leave Repeat daily checked.
- Press Add alarm. The list now shows “06:30 — Work — rings in Xh Ym”.
- Keep this tab open with the volume up. At 06:30 a full-screen banner appears and a synthesized bell rings; press Snooze 5 min or Stop.
Example 2 — Time zone converter: 3:00 PM Jakarta to London and New York
It is 3:00 PM in Jakarta (UTC+7) on January 15. Jakarta is 7 hours ahead of UTC, so first subtract: 15:00 − 7:00 = 08:00 UTC. Now apply each city's January offset:
- London is on UTC+0 in January → 08:00 + 0:00 = 8:00 AM.
- New York is on UTC−5 in January → 08:00 − 5:00 = 3:00 AM (same calendar date).
- Sydney is on UTC+11 in January (southern summer DST) → 08:00 + 11:00 = 7:00 PM.
Repeat the same meeting on July 15 and DST changes the answers: London is on UTC+1 → 9:00 AM; New York is on UTC−4 → 4:00 AM; Sydney is back on standard UTC+10 → 6:00 PM. This is exactly the kind of seasonal trap the world clock handles for you — add the cities once and read the live cards instead of doing the arithmetic.
Example 3 — Time running splits with the stopwatch
A runner wants 400 m splits during a 1,600 m session. Press Start, then Lap at the end of each 400 m. The lap table records two numbers per lap:
- Split — the time for that lap alone (for example 1:15.43, then 1:14.02).
- Total — elapsed time since you pressed start (1:15.43, then 2:29.45).
Compare splits to spot fading pace; the total tells you the projected finish. Because the stopwatch is timestamp-based, checking your phone mid-run costs you zero accuracy.
Practical tips
- Classroom clock online and exam timer online: use the Fullscreen button on the Clock tab for a display readable from the back row, and pair it with the Timer tab for visible countdowns.
- Kitchen timer online: the 1–60 minute presets with a loud alarm work perfectly for cooking — no app needed.
- Presentations and livestreams: full-screen mode doubles as a presentation timer clock or a clock for livestream overlays.
- Reliable alarms: keep the tab in the foreground, volume up, and disable auto-sleep while an alarm is armed. Browsers cannot sound an alarm from a closed tab.
- International meetings: add every participant's city to the world clock a day before, and glance at the cards instead of converting in your head — DST changes the math twice a year.
- 24-hour format removes all AM/PM ambiguity from schedules; one tap on the 12/24h button switches.
- Tab-title timer: the countdown mirrors into the browser tab title, so you can monitor it while working in another tab.
- Keyboard-free operation: every control is a large touch target, so the page works well on phones, tablets, and shared touchscreens.
Scope note: this is a personal full-screen clock suite (clock, world clock, alarm, stopwatch, timer). If you need classroom presentation timers with interval training, pomodoro cycles, or noise monitoring, that is a different tool — our classroom timer suite covers it.
Frequently asked questions
Is this online clock free to use?
Yes. This online clock is 100% free with no sign up, no download, and no limits. The clock, world clock, alarm, stopwatch, and timer all run entirely in your browser.
How accurate is the time shown on this online clock?
The clock shows your device's system time, updated every second. On a healthy device the operating system keeps itself synchronized over the internet using NTP (Network Time Protocol), so the displayed time on this internet clock is typically accurate to well within one second. If your computer or phone clock is set wrong, this page will show that same wrong time — enable "set time automatically" in your device settings to fix it.
Will the online alarm ring if I close the tab or put my device to sleep?
No. A web page cannot run code after its tab is closed, and most devices suspend background tabs when the screen sleeps. For a reliable wake-up alarm: keep this tab open in the foreground, turn your volume up, and disable auto-sleep in your device's power settings while the alarm is armed. For critical wake-ups, use a dedicated alarm app or device as a backup.
How do I set an alarm online?
Open the Alarm tab, pick a time (for example 06:30), optionally type a label such as "Work", check "Repeat daily", then press Add alarm. The alarm list shows how long until each alarm rings. Toggle an alarm off without deleting it, or delete it with the × button. Alarms are saved in your browser, so they survive a page reload on the same device.
What is the difference between 12-hour and 24-hour time?
The 12-hour format splits the day into AM (midnight to noon) and PM (noon to midnight), so 3:05 PM is afternoon. The 24-hour format (sometimes called military time) counts 00:00 at midnight straight through to 23:59, so 3:05 PM becomes 15:05 — there is no AM/PM ambiguity, which is why schedules, transport, and aviation prefer it. Use the 12/24h button on the Clock tab to switch.
Why does the clock show a different time than I expect?
Almost always because of the device's time-zone setting, not this page. The clock renders your system time in your system time zone. If you recently traveled, or your operating system has the wrong region selected, every website will show that same shifted time. Check your device's date & time settings and make sure both "set time automatically" and the correct time zone are enabled.
What do labels like UTC+7 and UTC−5 mean?
UTC (Coordinated Universal Time) is the global reference clock. A label like UTC+7 means local time is 7 hours ahead of UTC — when it is 12:00 UTC, it is 19:00 there. UTC−5 means 5 hours behind UTC. Half-hour and 45-minute zones exist too: India is UTC+5:30 and Nepal is UTC+5:45, so their clocks never sit exactly on the hour relative to UTC.
Does the world clock adjust for daylight saving time automatically?
Yes. Offsets are computed live from the IANA time-zone database built into your browser, which includes every region's daylight saving rules. For example, New York shows UTC−5 in January and UTC−4 in July without you changing anything. Each world-clock card displays its current live UTC offset.
Can I use the full-screen clock in a classroom or during exams?
Yes. Press the Fullscreen button on the Clock tab for a full screen clock with huge high-contrast digits readable across a room — a free fullscreen clock — useful for classrooms, exams, presentations, and livestreams. The seconds display and date stay visible. If you need presentation-style countdowns with interval or pomodoro modes, our classroom timer suite is built for that instead.
Does the stopwatch keep running accurately if I switch browser tabs?
Yes. The stopwatch and timer are timestamp-based: they record a start moment with the system clock and compute elapsed time from it, instead of counting ticks. That means switching tabs, minimizing the window, or a busy CPU cannot make them drift. Laps record both the split (time since the previous lap) and the cumulative total.
Does this online clock work offline?
After the page has loaded once, yes: this online clock works offline: the clock, world clock, alarm, stopwatch, and timer all run with zero network requests, so they keep working if your connection drops. You only need the internet for the initial page load.
Is any of my data sent to a server?
No. Everything — your alarms, world-clock cities, and display preferences — is stored in your browser's localStorage on your own device. The page makes no network requests at all except loading itself, so there is nothing to intercept and nothing to leak.
Does this browser clock use NTP?
Not directly. Browsers cannot open the UDP connections NTP needs, so a browser clock cannot query time servers itself — it reads your operating system’s clock instead. Your OS does use NTP (that is what the “set time automatically” option does), typically keeping the system clock within tens of milliseconds of true time. So the chain is: NTP server → your OS clock → this page, refreshed every second.
Free tool by NRTechStudio