This is handled by creating 2 top level categories. "Lunch" & "Dinner" or "Lunch" & "All Day".  The sub categories/items will be listed under these top level categories and the top categories need to have a time restriction set on them (ex. Lunch category can have 11am to 3pm etc..).

Customers will only be able to order from the Lunch category (Lunch pricing) during the time restriction hours & won't be able to order outside of it. After the time has passed they will be forced to order from the Dinner/Regular pricing menu.

This method also can be used to offer different pricing during Breakfast hours/Breakfast menu as well. Setting a time restriction on the menu.