Last restart/start time of a windows service

If the server (or any Windows computer) is joined to a domain it will synchronize it's time automatically from the domain, and the Internet Time tab will disappear.

If the server is configured as an Active Directory domain controller, it should also be running a DNS service for the internal clients.

Your client machines should be using the address of the domain controller as their DNS server (the server should be pointing at itself for DNS). You'll then need to configure the DNS service on your domain controller to forward anything it can't resolve to your router.

If you want to switch it to a workgroup then you should be able to use Network Discovery for local name resolution, but personally I'd keep the domain.