Information
The PASS_WARN_AGE parameter in /etc/login.defs allows an administrator to notify users that their password will expire in a defined number of days. It is recommended that the PASS_WARN_AGE parameter be set to 7 or more days.
Providing an advance warning that a password will be expiring gives users time to think of a secure password. Users caught unaware may choose a simple password or write it down where it may be discovered.
Solution
Set the PASS_WARN_AGE parameter to 7 in /etc/login.defs :
PASS_WARN_AGE 7
Modify user parameters for all users with a password set to match:
# chage --warndays 7 <user>