Kevin Eckart shows you users with recent password changes:
There may come a time when you need to generate a list of SQL logins and the last time their password was changed. By using the LOGINPROPERTY of the name in sys.server_principals we can generate such a list.
Note: This will only work with SQL logins.
If you want (or need) to know that passwords are being updated but can’t turn on password policies, this at least answers the initial question.