login/password_expiration_time is a SAP Parameter attribute which is used to control Dates until password must be changed information. This is available within R/3 SAP systems depending on the version and release level.
Below is the standard documentation available and a few details of the attributes values .
The value 0 indicates that no users are forced to change their
passwords.
Values greater than 0 specify the number of days after which users need
to change their passwords. (Exception: Users of the types SERVICE and
SYSTEM).
See SAP Parameter Documentation for full SAP documentation for this profile parameter.