My guess would be in the tasks-xyz-.xml files located in <CAS Install>\config. You would be looking to change the 'offset' time, but I would want someone else to verify before I send you down that path for certain. I will keep looking into this on my end and see if I can come up with anything better.
That is a bit complicated and I'm not sure if anyone have tried it before.
Baselines are computed during an execution of BaselinesImpl command (file tasks-400-rtm.xml) that is a part Daily report generation task (file tasks-100-hcbs.xml). As we cannot set different time offsets for commands it would require separating the command to single (new) task.
As said it has not been tested but if you with we can elaborate how to do it. Plus, after each Service Pack the changes will be reverted.
What makes you to do the change?
I think I have to change the values for daily report generation. But I dont know how it works. The problem is that we need to change the CAS processing for baselines calculation from 12:00 AM to 3:00 AM to avoid conflict with other process that the client run at that time.