I've seen this myself but never done it.
A client asked...
>>What will it cost to make this a live website. One where visitors stop in they will know it's closed at 5:00 Monday to Friday and 12 NOON on Saturdays. Closed on Sundays. I've seen this and it would really help me from receiving calls all hours of the night. <<
Not sure if she means something else but the only place I've seen this is in Google Search Results. How is it done?