Microsoft Windows Update schedule

you cannot set a specific time for a restart. If you choose AUoptions 4 - "Auto download and schedule the install" it will install patches at the set time and day of the week (there is no possibility to choose day of the month either...) Then it depends on how long the installation will take and server will just reboot if the update requires it. Also the configuring phase after reboot can take long time and usually much longer then the phase before reboot (especially on w2k16 servers).

There are however some options like "No auto-restart with logged on users for scheduled automatic updates installations" so it will show a fullscreen message notifying user that restart is needed and they can can keep delaying it.

https://docs.microsoft.com/en-us/windows-server/administration/windows-server-update-services/deploy/4-configure-group-policy-settings-for-automatic-updates