Most of the applications users became INACTIVE

I have faced a strange issue with Oracle application R12.

1. All the fnd users status had been changed to "INACTIVE" except sysadmin.

2. Some of the responsibilities are unable to view and assign.

3. Unable change the password for the INACTIVE users.

Reason :

We have faced some hardware failure in the server before this issue arised.

Due to this, system administrator forgot to set time zone properly in server.

Solution :

We need to change the timezone of the server to keep current date in the server.