The year was 1924 when the Dutch government deiced to change some laws and organise a road race. Next year, it happened for real on July the 11th in 1925, on a track that was 28.4 kms long. Its success made the organisers feel the need of making it an annual event. In 1936 the event got the name of Dutch TT and was officialy registered.
The Dutch TT didn't take place between 1940 and 1945 because of the Second World War, but it did take place in 1946. In 1949 the FIM launched the official World Championship for motorcycles and Dutch TT has been a part of the MotoGP calendar since then.
Assen is also the only Grand Prix in the world to be held on a Saturday. It is said that there was a church near in start/finish line and it was impossible for the church goers to attend the Sunday meeting because of the closed roads. This forced the authorities to hold the race on Saturday and it proved to be a huge success, and stayed as a tradition.
"The reason why it was on the Saturday is that the church was near to the start/finish area. The town council didn’t want to have a situation in which people who wanted to go to church on a Sunday could not, as all of the roads were closed for the race. That is the reason the race was staged on the Saturday. That proved a success, so we continued to do it on the Saturday. It is now a real tradition to have the Grand Prix on the Saturday, but all other races at the circuit on a Sunday," explains Egbert Braakman, who was the Race Secretary at Assen between 1970 and 2006.