How to make the Screen Saver only activate at certain time??

[wailoon.ho]

How to set the screen saver only activate during day time?? Night time screen saver will be deactivated??

 

[Mumford]

There may be easier ways to do this, but off the top of my head the way I'd do it is to set up a cron job to modify the Screen Saver preference directly:

Here's the command:
$ defaults -currentHost write com.apple.screensaver idleTime 0

0 will cause the screen saver to never activate. To set the screen saver back to 30 minutes (1800 seconds), use:
$ defaults -currentHost write com.apple.screensaver idleTime 1800