Clock Accuracy Check
A transparent, approximate comparison—not an atomic-clock certification
Device clock check
Five small same-origin requests compare this device with the timestamp on CurrentTime.io’s CDN response. The lowest-latency sample is used.
This is a coarse diagnostic, not a traceable calibration. HTTP dates have one-second resolution, network transit is asymmetric, and CDN clocks can differ from national standards. Do not use this result for navigation, trading, legal deadlines, experiments, or other safety-critical timing.
What this check measures
Your browser records a local timestamp before and after each request. The server’s HTTP Dateheader is compared with the request midpoint. Of five probes, the result with the shortest round trip is kept because it was least exposed to network delay.
The uncertainty includes half of that round-trip time plus half a second for the header’s one-second resolution. Internet traffic is not perfectly symmetric, so the real error can be larger.
What it does not measure
- It does not connect directly to an atomic clock, NTP server, GPS receiver, or national laboratory.
- It cannot certify the CDN clock or compensate exactly for asymmetric network delay.
- It is not suitable evidence for compliance, legal disputes, experiments, trading, aviation, or navigation.
- A large offset is a prompt to check your operating system’s automatic date-and-time settings.