Let's say I'm in a corporate network where the NTP protocol is blocked, the BOFH^H^H^H^H sysadmins won't unblock it, and they didn't bother to set up a good internal NTP server. What's a good source that provides time via HTTP/HTTPS?

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2 Answers

You can use HTTP Time Protocol / htpdate. It's not a good source, not compared to NTP.
Other options include connecting a GPS-receiver or using a dialup modem.

Personally I would complain about the sysadmins to your boss. Correct time is important if you want to accurately judge HTTP cache timeouts and other time-sensitive things

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ANY web server provides the date in the headers of the response, with seconds precision.

You could just access a reputable web site such as and trust they keep their clock sane. If you want to be super-sure you can probe multiple sites.

Using https has a benefit over NTP - it is secure!

There is actually a standard in the works for getting time accurately and securely from web servers by using multiple, timed requests:

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