The International Isle of Man TT Race is an annual motorcycle sport event run on the Isle of Man in May or June of most years since its inaugural race in 1907.The Isle of Man TT has been traditionally run in a time-trial format on public roads closed for racing by the provisions of an Act of Tynwald . The event consists of one week of practice sessions followed by one week of racing. It has been a tradition perhaps started by racing competitors in the early 1920s for spectators to tour the Snaefell Mountain Course on motorcycles during the Isle of Man TT on "Mad Sunday," an informal and unofficial sanctioned event held on the Sunday between 'Practice Week' and 'Race Week.'The first Isle of Man TT race was held on Tuesday 28 May 1907 and was called the International Auto-Cycle Tourist Trophy. The event was organised by the Auto-Cycle Club over 10 laps of the Isle of Man St John's Short Course of 15 miles 1,470 yards for road-legal 'touring' motorcycles with exhaust silencers, saddles, pedals and mudguards.From 1911 the Isle of Man TT transferred to the much longer Snaefell Mountain Course of 37.40 miles . The race programme developed from a single race with two classes for the 1907 Isle of Man TT, expanding in 1911 to two individual races for the 350cc Junior TT motor-cycles and the Blue Riband event the 500cc Senior TT race. The race did not take place from 1915 to 1919 due to the First World War. It resumed in 1920. A 250cc Lightweight TT race was added to the Isle of Man TT programme in 1922 followed by a Sidecar TT race in 1923.