Determining last login time for a user

This should be simple but it's causing me heartburn. I just want to know the
last time any of the users on my Tru64 Unix V5.1B system have logged in. The
system shows it when you actually log in so I know it's there somewhere. I
want to do this from a system management (root) level so I can look to get
rid of accounts that haven't been used in a long time.

I tried the lastlogin command. It did create a file called
/var/adm/acct/sum/loginlog, but the first column (presumably the date) is
all zero's. I tried parsing my way through /var/adm/wtmp and it doesn't even
seem like all the information is there, but in any case, it's very hard to
read.

thanks!

Chris