Well if the NTP is working, and therefore the authentication, when you change the clock on the server you should soon have the clients altering their clocks to match.

The “xntpd” service – for clients of the machine to be able to use the machine as a time server - is configured as follows.

Edit “/etc/ntp.conf”, comment out "broadcastclient" with a "#":

#broadcastclient
driftfile /etc/ntp.drift
tracefile /etc/ntp.trace

Add the following lines pointing to the machine itself:
server 127.127.1.0 prefer               # 10.X.X.X - self
fudge 127.127.1.0 stratum 0             # values for local clock
keys /etc/ntp.keys                      # where the keys are
trustedkey 15                           # keyid's we trust
requestkey 15                           # keyid for mode 7 requests (xntpdc)
controlkey 15                           # keyid for mode 6 requests (ntpq)
enable auth                             # turn on authentication
#broadcast xxt.xxx.xxx.xxx              # turn on broadcast


Create the file “/etc/ntp.keys”, based on the sample file provided “/usr/samples/xntp/example.keys”.  Change the key values to your own password-like entries:

2    M   admin
15   M   root