Newscasts, also known as bulletins or news program(me)s, differ in content, tone, and presentation style depending on the format of the channel/station on which they appear, and their timeslot. In most parts of the world, national television networks will have bulletins featuring national and international news. The top-rated shows will often air in the evening during "prime time", but there are also morning newscasts of two to three hours in length. Rolling news channels broadcast news content 24 hours a day. The advent of the internet has allowed the regular 24-hour-a-day presentation of many video and audio news reports, which are updated when additional information becomes available; many television broadcasters provide content originally provided on-air as well as exclusive or supplementary news content on their websites. Local news may be presented by standalone local television stations, stations affiliated with national networks or by local studios which "opt-out" of national network programming at specified points. Different news programming may be aimed at different audiences, depending on age, socio-economic group, or those from particular sections of society. "Magazine-style" television shows (or newsmagazines) may mix news coverage with topical lifestyle issues, debates, or entertainment content. Public affairs programs provide analysis of and interviews about political, social, and economic issues.