Shelly off-line

Have set up a Shelly device with Home Assistant on a Raspberry Pi - all works fine. For operation I'd like to ensure that the local lights will work even when the Internet is down. In my set up both the Shelly device as well as the Raspberry PI have a static IP address. When switching on without web access I am referred to the fact that the Shelly device needs an SMTP Server to synchronize the time. Is there a way to have the Shelly devices obtain the time from the Raspberry Pi rather than from the web? or do I have to set up an STMP Server on the Raspberry Pi?

In case the question was posed alredy, please just send the link and I'll go through that thread.