Q: How can I schedule a scan in specified time?

A: At first - keep on mind that this feature (scheduler) is in PROFESSIONAL edition of avast! only; it´s not available in HOME edition. If you have the PROFESSIONAL edition, start avast! in enhanced interface, in left pane click on SCHEDULER. Then click on Scheduler in tool bar, from the menu choose "create event" and specify the scan type, period and so on as you wish.