for patches,
The Install date on the system is pointless. It is more important to reference the exact patch to see if there is an alert on it.
the patches are in xxxxxx-xx format
eg: 118844-29
When you search sun alerts, it will tell you specifically what patch and revision it is reporting about. So if there was a Sun Alert on 118844-29, it would show that specifically, if you seen 118844-29 in the Sun alert, and you had -37 installed than your patch revision is not affected.
You can use the command: showrev -p to see what patches are installed on your server:
#showrev -p (gives you all patches, really noisy)
#showrev -p |grep 118844
#showrev -p | grep "Patch: 118668"
You can find some patches located in /var/sadm/patches, you will not find all the patches there though, the only patches in this directly for the most part are the patches that make up the core operating system and kernel updates.
So using the showrev command is more accurate.