Must have e71 softwares

http://www.symbian-freeware.com/download-profile-scheduler.html
Profile Scheduler is a free Profile scheduler application that allows automated profile changing with timer scheduling.

http://www.symbian-freeware.com/download-theme-scheduler.html
Summary: Theme Scheduler is a free theme scheduler application that allows automated theme schduling with timer, or automated theme changing according to active profile.

Now you don't have to remember switching your phone off/ put to silent mode at night to prevent calls from disturbing your sleep.