Forcing password reset after first login?

There is the Password_Update_date field in the user_id table, then there is the and system parameter PasswordResetTime which we have set to 90 days. Can we manipulate these two to force the users to change their password after their first login? The thought is to update their Password_Update_date to about 80 days before the go-live date, then when the user logs in for the first time after go-live, they should be prompted about the pending password expiration and will proceed to change the password. According to dmtig "Warnings will be sent within 10 days of the reset deadline", however when