Indeed, it is there just like TrickyKid said. And it is accessible via the 'last' command just like it is under Linux.
When did this become a Solaris forum?
adm/lastlog
This binary log file stores information about a user who has logged into the system. It is kept up to date by utilities such as login(1) and in.uucpd(1M). The data are viewable with tools such as last(1), who(1), and finger(1). Refer to the system man pages for more information.