The HTTP Time Protocol (HTP) is used to synchronize a computers time with web servers as reference time source. This program can be used instead of ntpdate or similar in networks that have a firewall blocking the NTP port.

Htpdate will synchronize the computer time to Greenwich Mean Time (GMT), using the timestamps from HTTP headers found in web server responses (the HEAD method will be used to get the information).

Htpdate works through proxy servers. Accuracy of htpdate will be usually within 0.5 seconds (better with multiple servers).

To allow the snap package to adjust the time you need to connect the time-control interface after installation and restart the daemon:

 snap connect htpdate-daemon:time-control

. You can set the list of hosts (default: google.com) to query for time via a snap setting like:

 snap set htpdate-daemon hosts="google.com www.linux.org"

You can also set additional options for the daemon

 snap set htpdate-daemon extra-opts="-d"

It is recommended that you disable your hosts ntp time sync mechanism when using htpdate-daemon.