Atomic Clock + World Time

A server-calibrated clock with stable smoothing, multiple styles, clock-only fullscreen mode, and a world time board

Tool

Precision time, easy setup

Atomic Clock

Server-calibrated precision clock + world time (privacy-first)
Local device time Local Shortcuts: F, C, T, 1–4
World Time
Times follow the calibrated clock. Edit cities in Settings.

Clock Settings

Clock style
choose one
Theme
5 presets
Themes are tool-local and respect the site’s Light/Dark mode.
Main clock time zone
device region by default
Advanced settings
The clean link stays short. Share links encode settings in the URL hash (client-side). No server storage.

Description

UTC at a glance

This tool renders a high-precision “atomic-style” clock in your browser and calibrates it using a same-domain server time endpoint. The client measures round-trip time (RTT), estimates the midpoint, computes a time offset, and applies smoothed corrections for a stable display (no jumpy time).
Below the clock is a full-width World Time board for common cities and your own selections. You can add, remove, and reorder cities inside the Settings popup, and share your exact configuration via a URL hash link. Fullscreen mode is optimized for presentation: only the clock is shown, large and clean, with a simple X button to exit.
  • Atomic clocks (high level): Atomic clocks keep time by measuring extremely consistent atomic transitions—famously the cesium-133 standard that defines the SI second. Most people access “atomic time” indirectly through time services that distribute UTC.
  • UTC + why sync matters: Device clocks drift. By pinging a local server time endpoint and accounting for RTT, the tool estimates an offset and keeps the display aligned to a consistent reference. Smoothing makes the display stable even when network conditions vary.
  • World time: practical value: World clocks reduce mistakes in scheduling, travel planning, classroom demos, streaming overlays, and cross-market timing.
  • Practical presets:
    • Travel: simplified view + key destinations
    • Trading: UTC-centric + high-contrast + milliseconds
    • Remote Team: distributed cities + clear readability
    • Classroom: analog-friendly teaching view
    • Streamer/OBS: big clock focus + minimal date
  • Privacy & data handling (privacy-first):
    • Browser: renders the clock and formats time zones using the Intl API. If enabled, settings can be stored in localStorage on your device.
    • Server: provides only a minimal time ping (UTC timestamp + microseconds) for calibration.
    • Not stored: no accounts, no analytics in this tool, no city lists saved on the server, no database writes, no trackers.
    • Share links: settings are encoded in the URL hash (client-side). Nothing is uploaded.

Similar tools (Data)

Explore more helpers from the same category.

Current ISO Week

Show the current ISO week number with a clean fullscreen display for TVs — theme switch (T) with live preview and automatic daily updates.

5.00 / 5 · 1 reviews
Open

Text to Speech

Local-first Text-to-Speech tool with voice selection, language filtering, sliders, optional chunking, and reliable controls — now with a clean, closable settings popup.

New · be the first
Open

FAQ

Frequently asked questions