modify the scan schedule from sepm for weeky to daily mid night?

Check it

How to schedule a scan from the Symantec Endpoint Protection Manager console

##Edit##

https://www-secure.symantec.com/connect/forums/unable-change-scheduled-scan-timings 

1.Open the Symantec Endpoint Protection Manager.

2. Select Policies from the far left.

3. Highlight Antivirus and Antispyware under the View Policies section in the middle column.

4. Highlight the active policy from the right side of the manager.

5. Click Edit the Policy under the Tasks menu is the middle column.

6. A new window will open.

7. Select Administrator-defined Scans from the far left menu in the new window.

8. Select the Schedule  tab. and chnage the time accordingly

Set the time which you require to configure

You can modify it to any schedule you like.. facing any issue?

Go into your AV policy under Administrator-Defined Scans and edit your current scan as you see fit. It's very straightforward....

To find basic help please refer knowledge base: http://www.symantec.com/business/support/index?page=content&key=54619&channel=TECHNICAL_SOLUTION