SELECT count(*) ,  time_of_day FROM broadcast GROUP BY time_of_day
how many programs are broadcast in each time section of the day?
[Schema (values) (types)]: | program_share |  program : program_id (text) , name (number) , origin (text) , launch (text) , owner (number) | channel : channel_id (text) , name (number) , owner (text) , share_in_percent (text) , rating_in_percent (number) | broadcast : channel_id (text) , program_id (number) , time_of_day (text) | broadcast_share : channel_id (text) , program_id (number) , date (text) , share_in_percent (text);