You are very welcome to add opening hours to your POIs!
Opening hours can be used in a filter, where a user wants only to show POIs right open now. (e.g. like on osm24.eu )
However, as opening hours can be very complex (imagine the third last Tuesday in Months Apr-Sep.) we will use the Scheme used by OpenStreetMap. It looks simple (e.g. “Mo-Fr 08:00-15:00”), but is very powerful.