This policy setting allows you to specify the day of the week on which to check for definition updates. The check can also be configured to run every day or to never run at all. This setting can be configured with the following ordinal number values: (0x0) Every Day (default) (0x1) Sunday (0x2) Monday (0x3) Tuesday (0x4) Wednesday (0x5) Thursday (0x6) Friday (0x7) Saturday (0x8) Never If you enable this setting, the check for definition updates will occur at the frequency specified. If you disable or do not configure this setting, the check for definition updates will occur at a default frequency. Fix: (1) GPO: Computer Configuration\Administrative Templates\Windows Components\Windows Defender\Signature Updates!Specify the day of the week to check for definition updates (2) REG: HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows Defender\Signature Updates!ScheduleDay