Clock Accuracy Test
Measure server time repeatedly, select low-latency samples and estimate whether your computer or phone clock is fast or slow, including test quality and network uncertainty.
About this tool
Measure server time repeatedly, select low-latency samples and estimate whether your computer or phone clock is fast or slow, including test quality and network uncertainty.
Use the tool above first; keep original inputs or files when the result matters, and verify the output in the destination system when there is a strict requirement.
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Worked example and limits
An HTTP Date reading of 12:00:00 carries only second resolution; it cannot establish a 20 ms device error. The tool estimates the interval center as 12:00:00.500. With an 80 ms round trip, uncertainty is about ±540 ms. This is a calculation example, not a measured network benchmark. Use operating-system time synchronization to correct persistent drift; the page cannot set the system clock.