Customers like quick replies when they contact you. Using this zap, which triggers on an inbound message, you can detect if it's out of office hours and send a reply.
The trigger of this zap doesn't matter. It can be an inbound email or a form submission.
The next step in the zap needs to be a Formatter step to convert the message received time into the HH time format.
Next you add a filter that only continues if the current HH time is not in a list of opening hours, also represented as HH.
In the final step, you can then send the customer an email using the built in "Email by Zapier" step or any other email app.