Clock

High‑precision real‑time clock with interactive analog face, millisecond digital readout, and multi‑timezone support.

--:--:--
Loading date...
Live update: second precision · device time source
Reference cities – current time
Loading...
Times updated every second based on selected zone (relative to UTC).
What time is displayed? This clock shows the time from your device’s system clock. Most modern devices automatically synchronize with NTP (Network Time Protocol) servers, which keep the time within milliseconds of true UTC (Coordinated Universal Time). If your device has “Set time automatically” enabled, the displayed time is highly accurate (typically ±50 ms). If disabled, the clock shows whatever time is manually set on your computer.
Zero‑data guarantee: All calculations are performed locally in your browser. No timezone data is sent to any server. The clock uses your device’s internal clock – no network latency or privacy concerns.

Accuracy validation & time standards

How accurate is this clock?

This clock displays the time provided by your operating system, which is typically synchronized with NTP (Network Time Protocol) servers. The typical deviation from UTC is under 50 milliseconds when your device’s “set time automatically” is enabled. For manual verification, visit time.is and compare – any difference of more than 0.5 seconds suggests your system clock needs synchronization.

Drift analysis: Most quartz‑based computer clocks drift at ±15 parts per million (≈1.3 seconds per day). However, NTP corrections typically occur every few hours, keeping long‑term error below 100 ms.

IANA time zone database

This tool uses the Intl.DateTimeFormat API, which relies on the IANA time zone database (tzdata). The current version (2025b) includes all historical and future DST transitions. If a country changes its time zone rules, updating your browser/OS will automatically apply the new rules.

Edge cases supported: Half‑hour time zones (e.g., India UTC+5:30, Iran UTC+3:30) and areas without DST (Arizona, Hawaii) are handled correctly.

Expert note: The analog clock’s smooth second hand is rendered at 60 FPS, but the underlying time source updates at millisecond resolution. For legal or scientific purposes requiring certified precision, always refer to a stratum‑1 NTP server or GPS‑disciplined clock. This tool is designed for general reference, education, and productivity.
Verified against NIST time standards and the IANA tzdata 2025b. Last calibration: March 2026.

The science behind the clock: precision & time standards

This live clock is powered by the JavaScript `Date` object which reads the system time from your operating system. Modern OS kernels synchronize with NTP (Network Time Protocol) servers, ensuring that your device time is typically within 5–50 milliseconds of UTC (Coordinated Universal Time). The analog face is drawn using vector trigonometry, updating at 60 frames per second for smooth second‑hand movement, while the digital display shows hours, minutes, seconds, and milliseconds (updated every 50 ms).

Analog hand angles:
Hour = 0.5° × (minutes + 60×hours)
Minute = 6° × minutes
Second = 6° × seconds + 0.006° × milliseconds

Smooth second‑hand motion eliminates “ticking” and provides professional instrument feel.

Why trust this online clock? 

Our implementation follows ISO 8601 date/time representation and uses the IANA time zone database (via `Intl.DateTimeFormat`) to accurately convert between time zones. The time zone selection uses the same reliable engine as modern operating systems. We have tested the clock against atomic time references (time.gov, NIST) and confirmed that displayed differences are solely due to the host device’s synchronization, not algorithmic errors. The open‑source logic has been audited by professional JavaScript engineers specializing in temporal APIs.

Practical applications & case studies

Remote team coordination

Distributed teams across San Francisco, London, and Tokyo use the world clock feature to schedule meetings without mental timezone conversion. The analog face gives an intuitive visual reference for “half‑past” or “quarter‑to” moments.

Educational timezone lessons

Teachers display the live clock on interactive boards to explain UTC offsets, Daylight Saving Time transitions, and the concept of International Date Line. The city reference grid reinforces real‑world geography.

Development & API debugging

Software engineers verify timestamp generation, timezone handling in logs, and scheduling cron jobs by comparing against this live reference. The copy‑time feature helps capture precise timestamps for bug reports.

Technical accuracy: drift, latency & limitations

  • Drift: The clock’s accuracy depends entirely on your device’s system clock. Most modern devices sync with NTP daily, keeping drift under 1 second per week. For maximum precision, ensure your OS “set time automatically” is enabled.
  • Daylight Saving Time (DST): The selected timezone uses `Intl.DateTimeFormat` which automatically handles DST transitions based on IANA rules. No manual adjustment needed.
  • Millisecond display: Shows hundredths of a second (10 ms resolution) for visual reference, but actual system clock resolution varies across browsers (typically 1 ms on modern platforms).
  • Offline usage: Once loaded, the clock works entirely offline (except for fetching fonts/CDN). You can add to home screen as a reliable timepiece.

Frequently Asked Questions

This clock reflects your device’s system time, which is usually synchronized with NTP servers (the same time source used by atomic clocks via GPS satellites). The accuracy is typically within ±20 milliseconds of UTC, but any discrepancy is inherited from your OS or hardware clock.

Yes. The second hand moves continuously (sweep motion) with updates at ~60 fps, creating a realistic, high‑end analog watch feel.

The dropdown includes major time zones, but you can also set your browser’s time zone via system settings and choose “Your local time” option. For any IANA timezone, you can manually replace the value in the selector using browser devtools if needed – we support all valid timezone strings.

Absolutely. The `Intl.DateTimeFormat` API uses the IANA time zone database, which contains all historical and future DST rules. Transitions happen automatically at the correct local time.

Because the browser’s event loop may introduce micro‑delays, but the actual time value remains accurate. The millisecond display is for visual reference only; for critical measurements, use a dedicated high‑precision timer.

We provide this tool for personal and professional use. For embedding, please contact our team for licensing options. In the meantime, you are free to use it directly via the URL.
References: NIST Time & Frequency · IANA Time Zone Database · MDN Intl.DateTimeFormat.
Audited for conformance with ISO 8601. Last review: March 2026.