47 CFR 73.1730: Specified hours.

(a) Specified hours stations must operate in accordance with the exact hours specified in their license. However, such stations, operating on local channels, unless sharing time with other stations, may operate at hours beyond those specified in their licenses to carry special events programing. When such programs are carried during nighttime hours, the station's authorized nighttime facilities must be used.

(b) Other exceptions to the adherence to the schedule of specified hours of operation are provided in § 73.72 (Operating during the experimental period), § 73.1250 (Broadcasting emergency information) and § 73.1740 (Minimum operating schedule).