Atomic Clock Online
Current atomic clock time with milliseconds, synchronized to UTC. Shows exact atomic time across all major time zones with DST status, TAI offset, and copy options.
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
About This Atomic Clock Display
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 atomic clock actual time down to the millisecond, synchronized to your device's NTP-disciplined system clock.
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; it counts SI seconds uninterrupted.
DST Indicators
Time zones currently observing Daylight Saving Time show a gold "DST" badge. DST advances the clock 1 hour forward in spring and sets it back in autumn, meaning the offset from UTC changes seasonally. Atomic clocks themselves are not affected by DST — only civil time displays change.
24-Hour Atomic Clock
All times are displayed in 24-hour atomic clock format (ISO 8601 / military time). This eliminates AM/PM ambiguity and matches the format used by NIST, ITU, and all scientific timekeeping standards. Midnight is 00:00:00, noon is 12:00:00, and 11 PM is 23:00:00.