"Downton Abbey" season one premiered on PBS in the United States on January 9, 2011. It was aired as part of the 40th season of the PBS program "Masterpiece".
Downton Abbey had previously aired in seven episodes on ITV, in the United Kingdom, starting on September 26, 2010. In the United States, the first season was broadcast in four 90-minute episodes, which required the beginning and end of each episode to by slightly altered due to timing issues and a lack of commercials. Subsequent seasons have more closely followed the ITV episode format, with eight episodes per series and a Christmas Special.