Atomic Clock Time Now
The most accurate online atomic clock — displaying the current UTC time with milliseconds, TAI offset, Unix timestamp, and live local times for all major time zones with DST status. Free, always accurate, no account needed.
This atomic clock online display synchronizes to your device's NTP-disciplined system clock and updates every 50 milliseconds, giving you the most precise time display possible in a browser. It shows UTC (Coordinated Universal Time), TAI (International Atomic Time), Unix epoch timestamp, and the current local time in 12 major time zones worldwide.
The display is used by developers who need precise timestamps, by scientists and researchers who need accurate UTC, by traders and financiers tracking global market open times, and by travelers checking the exact current time anywhere in the world.
Unlike standard clocks that rely solely on your browser, this display shows the TAI offset (+37 seconds ahead of UTC as of 2017) and notes whether each time zone is currently observing Daylight Saving Time — so you can see the correct civil time for any location, not just the raw UTC offset.
Want to see what time it is in multiple cities? Use our World Clock Widget. Need to find the best meeting time across time zones? Try the Meeting Planner.
This display shows current atomic time synchronized to your browser's system clock. For official atomic clock exact time, see time.nist.gov.
Atomic Clock Time by Zone
What Is an Atomic Clock?
How Atomic Clocks Work
An atomic clock measures time by tracking the electromagnetic frequency of atomic transitions. When a cesium-133 atom transitions between two energy states, it emits or absorbs microwave radiation at precisely 9,192,631,770 Hz. This frequency is so consistent that it forms the international definition of one second under the SI unit system.
The best atomic clocks today — optical lattice clocks using strontium or ytterbium atoms — are accurate to within 1 second in 15 billion years, roughly the current age of the universe.
Types of Atomic Clocks
Who Uses This Atomic Clock?
Developers & Engineers
Use the Unix timestamp for precise event logging, debugging race conditions, and cross-timezone timestamp validation in distributed systems.
Scientists & Researchers
Reference accurate UTC for data collection timestamps, experiment synchronization, and coordinating observations across global research teams.
Traders & Finance
Know the exact UTC time during market opens and closes worldwide. Track pre-market sessions across multiple exchanges simultaneously.
Travelers & Nomads
Check the exact current time in any major time zone instantly, including DST status, without doing mental math or checking multiple apps.
Why Use This Atomic Clock?
No account, no subscription, no ads blocking the clock face. Open the page, read the time.
The fastest refresh rate of any free online clock — shows seconds and milliseconds with near-real-time precision.
Zero friction. No email, no password, no cookie wall. Just the exact current time, immediately.
Your device's system clock syncs to atomic time servers continuously. This display reads directly from that synced source.
Every time zone shown reflects the actual current civil time, including Daylight Saving Time adjustments.
See 12+ major time zones simultaneously — from Los Angeles to Tokyo — in one clean display.
About This Atomic Clock Display
UTC vs. TAI
UTC (Coordinated Universal Time) is the civil time standard derived from atomic time. TAI (International Atomic Time) runs exactly 37 seconds ahead of UTC — the accumulated total of all 27 leap seconds inserted since 1972 plus the initial 10-second offset. TAI never has leap seconds and counts SI seconds uninterrupted.
Live Time with Milliseconds
The atomic clock real time display updates every 50 milliseconds, showing seconds and milliseconds in the large UTC clock face. This gives you the current atomic time down to the millisecond, synchronized to your device's NTP-disciplined system clock.
DST Indicators
Time zones currently observing Daylight Saving Time show a gold "DST" badge. DST advances clocks 1 hour forward in spring and back in autumn. Atomic clocks themselves are not affected by DST — only civil time displays change.
24-Hour Format
All times are displayed in 24-hour format (ISO 8601 / military time), matching the format used by NIST, ITU, and all scientific timekeeping standards. Midnight is 00:00:00, noon is 12:00:00, 11 PM is 23:00:00.
Need to Schedule Across Time Zones?
Use our free Meeting Planner to find the best overlap time for teams in any combination of cities, states, or countries — with a full 24-hour timeline visualization.