Configuring NTP for switches is a rather simple process, however the syntax varies depending on the switch OS.
Most switches use SNTP rather than NTP, SNTP is basically NTP but lacks some of the more advanced internal algorithms and is slightly less accurate.
To configure a ProCurve you need to use SNTP with the following syntax.
sntp server <ip> sntp unicast timesync sntp
The first line defines what IP to sync with, the second tells the switch to use unicast UDP rather than TCP and the third tells the switch to sync it's time with the SNTP server.
This needs to be done in configure mode which can be got into via enable mode.
Once the switch is syncing with the SNTP server you can check the time is correct with
Lastly just save the changes then logout
write mem logout
A full example of this is below:
Switch> en Switch# conf Switch(config)# sntp server 18.104.22.168 Switch(config)# sntp unicast Switch(config)# timesync sntp Switch(config)# exit Switch# write mem Switch# logout
Your switches should now keep their time in sync :)