BBC Radio 1 is one of the BBC's two flagship radio stations (the other being BBC Radio 2), specialising in modern popular music and current chart hits throughout the day. Radio 1 provides alternative genres at night, including electronica, dance, hip hop and indie. The choice of music and presenting style is entirely that of programme hosts, however those who present in the daytime have to rotate a number of songs a specific number of times (8, 13 or 15) per week. It was launched in 1967 to meet the demand for music generated by pirate radio stations, when the average age of the UK population was 27. The BBC claim that they target the 15–29 age group, and the average age of its UK audience since 2009 is 30. BBC Radio 1 started 24-hour broadcasting on 1 May 1991.