ok I think i've found what i'm looking for. Further hunting on sunsolve found the following:
#234461: Solaris Daylight Saving Time (DST) Update (Aug 2008, Oct 2008, Mar 2009)
The following patches should be installed for DST updates:
SPARC Platform:
* Solaris 8 with patch 109809-11 or later
* Solaris 9 with patch 113225-14 or later
* Solaris 10 with patch 138856-02 or later
x86 Platform:
* Solaris 8 with patch 109810-11 or later
* Solaris 9 with patch 116545-12 or later
* Solaris 10 with patch 138857-02 or later
If you check for the above patches, then use 'zdump -v' I think that should cover things ok.
Thanks to all.