The scoadmin tool is not overly helpful when setting up specific timezones, especially in OZ where daylight savings changes.

Its easier to edit the TIMEZONE file and setup the timed daemon to sync to a timed server. The timed daemon slowly skews the clock to get in sync, thus its recommended over ntp when using databases which may get all confused if the timed is suddenly changed drastically.

First edit /etc/TIMEZONE

Change your TZ value as such...

TZ=AEST-10AEDST,M10.5.0,M3.5.0 

Secondly create a script in /etc/rc2.d called S99timed. Assume you have already or will setup timed on a Linux server in your network.

# vi /etc/rc2.d/S99timed

add the following line

timed &

save and quit the file.

# chmod 755 /etc/rc2.d/S99timed

Then on your Linux timed server....

Install the rpm from here

Copy the initscript from here into the /etc/init.d directory.

# chmod 755 /etc/init.d/timed

# chkconfig --add timed; chkconfig timed on

Lastly create /etc/networks 

# vi /etc/networks

add the following to suit your subnet...

localnet 192.168.1.0

Save and quit.

# service timed start.

back on the Sco box...

# /etc/rc2.d/S99timed

Done.