Clock Accuracy Test & Methodology
iTime.live compares your device clock with a timestamp generated at a Cloudflare edge location. The result is useful for ordinary clock checks, but it is not a direct reading from PTB, NIST, GPS, or another laboratory clock.
Device Clock Accuracy Test
The test takes five samples and uses the lowest-latency response. It reports an estimate and an uncertainty range, not certified time.
How the estimate works
- The browser records when a request starts.
- The Cloudflare Pages Worker returns its current UTC timestamp.
- The browser measures the full round-trip delay and adds half of it to the returned timestamp.
- The test repeats five times and uses the lowest-latency sample to reduce queueing noise.
What the uncertainty means
The calculation assumes that the outward and return network paths take similar amounts of time. Real internet routes can be asymmetric, and the browser, operating system, and display may pause or schedule work. Half of the best observed round trip is therefore shown as an uncertainty estimate rather than hidden behind an “exact” claim.
UTC, NTP, and atomic clocks
UTC is the civil time scale used by internet systems. Atomic clocks contribute to international timekeeping, while NTP and other synchronization systems distribute time across networks. A web page only receives a network timestamp and cannot reproduce laboratory-level clock accuracy in a visitor’s browser.
Appropriate use
Use iTime.live for scheduling, timezone conversion, and checking whether an ordinary device clock appears noticeably fast or slow. Do not use it for legal timestamps, trading execution, navigation, scientific measurements, safety systems, or forensic evidence.