3 ms·

Maybe a silly question, but how can they reliably detect and display the error between my system time and the actual time? I would think there'd be some latency

Maybe a silly question, but how can they reliably detect and display the error between my system time and the actual time? I would think there'd be some latency introduced while the page is being loaded/drawn, and by the JavaScript code that's displaying/changing the time, among others.

kube-system 7y ago
Simple. Measure the latency, and then correct for it! > When a user connects to www.time.gov on a computer or mobile device, the Javascript in the client's browser checks the local clock on the device and then requests the time from a NIST server, which has been synchronized with UTC(NIST). When the packets containing the NIST time stamp arrive at the client's browser, the device clock is checked again and compared to the first check of the local clock. The result is a measurement the round-trip delay of requesting/receiving the time stamp. https://www.nist.gov/pml/time-and-frequency-division/about-timegov https://www.nist.gov/pml/time-and-frequency-division/about-t...
- StringyBob 7y ago
  > It is estimated that the one-half of the round-trip delay happens in each direction. Anyone know how true this is? Particularly for mobile/asymmetric bandwidth connections - what might the errors bars be?
eganist 7y ago
kube-system nailed it, though if you want to see the JS in action, visit https://time.gov/scripts/zzz__0fd3fed7f945928bf590af174cd541f0e02fce58.js https://time.gov/scripts/zzz__0fd3fed7f945928bf590af174cd541... and grep for realTimeDif
- winrid 7y ago
  Nice. No React or Angular here! Wonder if that's normal for government projects?
  - tatersolid 7y ago
    Yes, government things are usually required to work for more than a few years without requiring a total rewrite.