The episodes are each an hour in length, comprising the main programme and a 10-minute featurette called "Planet Earth Diaries", which details the filming of a particular event. In the UK, "Planet Earth" was split into two parts, broadcast in spring and autumn 2006. The first five episodes premiered on BBC One at 9:00 pm on Sundays, beginning on 5 March 2006. The programmes were repeated the following Saturday in an early evening slot on BBC Two. Along with its 2005 dramatisation of "Bleak House", the BBC selected "Planet Earth" for its trial of high-definition broadcasts. The opening episode was its first-ever scheduled programme in the format, shown 27 May 2006 on the BBC HD channel.