modifying date and time and time zone on solaris 5.10 with (redundant server) veritas

I have a cluster of two Solaris server (veritas cluster). one working and the other is standby
I am going to change the date on them , and am looking for a secure solution as it is giving an important service.
my opinion is that the active one doesn't need to be restarted (if I don't change the time zone )and just I need to change the date by date command .
but for the standby server i am looking for an instruction to chenge and sync them.
so please give your ideas to help.
thanks

How about both in sync with your time server?

How to Configure Network Time Protocol (NTP) (Sun Cluster Software Installation Guide for Solaris OS)

Otherwise make the active cluster member the time server for the standby.

An aside: it sounds like you are going to run the cluster "outside time and date". Meaning not synced to a real time/date server.
This is a bad idea. Please tell us what you are trying to do, not how you decided to do it. UNIX works on the presumption that the kernel clock is running UTC time. Example: This means filetimes are flat out wrong, so moving files off or onto the system from sources outside the cluster can create future dated files. e.g., Backup tape library systems like Simpana have issues with this.