I recently picked up a couple ProCurve 2910al-48G-PoE switches. Since it had been a while since is setup time on a switch I had to research a bit. Here are the settings I used.
First, you can view the switches current time, timezone, etc. with the show time command.
Next go into config mode (configure terminal) on the switch’s CLI.
sntp server priority 1 18.104.22.168
sntp server priority 2 22.214.171.124
time timezone -300
time daylight-time-rule continental-us-and-canada
Now, when I run show time the switch displays the current local time!