Oracle Database Discussions

I need to change the time of our Users Expiration Date. Not the date, just the time. For example, if the User's current Expiration Date is Jul 29, 2008 9:17:38 AM EDT, I would need to change it to Jul 29, 2008 1:00:00 AM EDT. Can anybody help me? I am pretty new to the DBA position and can't seem to figure this out.

Here is a little background, if you are interested. We have a 3rd party vendor application that uses an Oracle 10g db. The users login with their username and password from the Oracle db. If the user tries to login with an expired password, they are notified that they cannot login due to this expiration and sends them through the password change process. On the other hand, if a user logs in with a non-expired password that expires during their session, the application tries over and over again to access the db with the same expired username and password, eventually locking out the user. This causes alerts to be triggered in our MARS system indicating that a brute force login attempt may be happening. Every time this happens, we need to write a report for our auditors explaining what happened. Time Consuming. Since 99.9% of the time, our users login at the start of the business day, I think if we just changed all of the expiration times to happen in the middle of the night, we could avoid the vaast majority of our issues.

Thank you in advance for any feedback.