This policy setting allows you to enable or disable randomization of the scheduled scan start time and the scheduled definition update start time. This setting is used to distribute the resource impact of scanning. For example it could be used in guest virtual machines sharing a host to prevent multiple guest virtual machines from undertaking a disk-intensive operation at the same time.If you enable or do not configure this setting scheduled tasks will begin at a random time within an interval of 30 minutes before and after the specified start time.If you disable this setting scheduled tasks will begin at the specified start time.
Windows Components\Windows Defender
At least Windows Server 2012 Windows 8 or Windows RT