What is a Stratum-1 atomic time server?

In the hierarchy of global timekeeping, a Stratum-1 server is the highest-level internet time server available to the public. It is hardwired directly into Stratum-0 devices—which are actual physical atomic clocks, GPS satellite arrays, or national timing labs like NIST.

What is a Stratum-1 atomic time server?

In the hierarchy of global timekeeping, a Stratum-1 server is the highest-level internet time server available to the public. It is hardwired directly into Stratum-0 devices—which are actual physical atomic clocks, GPS satellite arrays, or national timing labs like NIST.

Stratum-1 Atomic Synchronization

Clock Accuracy Test & Time Synchronization Guide

Is your computer or phone clock fast or slow? Check your exact device time drift against official atomic time down to the millisecond, and learn how to fix it.

Device Synchronization Status

Measuring offset...

Estimated measurement accuracy: ±10 ms via NTP-synchronized server round-trip.

Calculated Drift0 ms

Atomic ReferenceUTC (NIST)

View Atomic Clock Full Screen Seconds

Hardware Clock Diagnostics

Is Your Computer or Phone Clock Fast or Slow?

If you are missing perfectly timed auction bids, experiencing login errors, or noticing your calendar notifications are slightly off, your device clock might be drifting. Computers and smartphones use inexpensive internal quartz oscillators to track time. Because these physical crystals are sensitive to heat and CPU loads, they naturally drift fast or slow over time. Our live hardware clock accuracy diagnostic tool instantly measures the exact millisecond difference between your device's internal clock and official atomic time.

If the diagnostic tool shows that your clock is running fast or slow, you can easily force your operating system to re-sync with global time servers.

For Windows 10 and 11: Open your start menu and go to Settings > Time & Language > Date & Time. Scroll down to 'Additional settings' and click the 'Sync now' button to align your PC with time.windows.com.

For Apple macOS: Open System Settings > General > Date & Time. Make sure the 'Set time and date automatically' toggle is turned on so your Mac syncs with time.apple.com.

For iPhone, iPad, and Android devices: The easiest way to fix mobile drift is to open your date and time settings, turn 'Set Automatically' off, and then immediately turn it back on. This forces your phone to pull a fresh NITZ time signal directly from your local cellular network towers.

How to Fix Clock Drift on Windows 10 & 11

Diagnose quartz oscillator drift caused by processor thermal throttling, CMOS battery aging, or NTP poll latency.

How to Sync Time on Apple macOS

Diagnose quartz oscillator drift caused by processor thermal throttling, CMOS battery aging, or NTP poll latency.

Automatic Time Updates for iOS and Android

Diagnose quartz oscillator drift caused by processor thermal throttling, CMOS battery aging, or NTP poll latency.

Frequently Asked Questions About Clock Accuracy

Common queries, time calculations, and scientific explanations

Google SERP Verified

Even though your browser can't talk directly to a physical atomic clock, we ping official Stratum-1 time servers. We measure the exact fraction of a second it takes for that signal to travel to your device (network latency) and compare it against your system clock, revealing your exact time drift down to the millisecond.