Visitor management sytem sign out


Hallo Airtable Experts,
I want to create a database for visitor registration. I started with the template visitor management system and i’m trying to set it up to sign out.
For example Steven Lodewijks come in on 7/11/2018 13:16 and leave the company on 7/11/2018 15:15.
Does anyone have an idea how to do that?
Afterwards it is then possible to calculate the present time.

Very open to ideas