How to configure NTP / SNTP on an HP Procurve switch
sntp unicast
timesync sntp
sntp server priority 1 1.2.3.4
Depending on the version, you may require a slightly different syntax
sntp unicast
timesync sntp
sntp server 1.2.3.4
Change the 1.2.3.4 to be the IP address of your NTP server. I often use domain controllers as an NTP server as they automatically run NTP.
Make sure you write the config to memory afterwards.
write mem