Then rerun the installer. This rolls back the system clock to 2016, bypassing the certificate check. After installation, reconnect Wi-Fi and sync the date automatically.
Once the installation media is created on the virtual disk, unmount it and use Disk Utility to "Convert" the file into a compressed Third-Party Sources macos high sierra 10.13.1 dmg
sudo /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/MyUSBDrive Then rerun the installer