hey @daichifj - I think I figured it out. When you create a new form in an app, click "customize initial values". Then, in your timestamp field, enter =Now() to insert the current date/time.
Hi @daichifj and @Jaso-8da0, welcome to the community! Yep, NOW() is the function to use here. What you could do is have a button on a screen with an automation (builder) associated with it. That automation will insert NOW() table columns, such as "coming time" and "leaving time." And then when the person clicks/taps the button, the automation will run and update the table(s).
There's a tremendous amount of flexibility with automations, so I recommend you experiment with it for this use case. Seems like it'll be a good fit.