HP ProCurve Management And Configuration Manual page 218

Time Protocols
SNTP Unicast Time Polling with Multiple SNTP Servers
Prioritized list of SNTP
Server IP Addresses
Figure 9-21. Example of SNTP Server Address Prioritization
N o t e
9-26
If there are already three SNTP server addresses configured on the switch,
and you want to use the CLI to replace one of the existing addresses with a
new one, you must delete the unwanted address before you configure the new
one.
Deleting Addresses. To delete an address, you must use the CLI. If there are
multiple addresses and you delete one of them, the switch re-orders the
address priority. (Refer to "Address Prioritization" on page 9-24.)
Syntax: no sntp server < ip-addr >
For example, to delete the primary address in the above example (and
automatically convert the secondary address to primary):
ProCurve(config)# no sntp server 10.28.227.141