The Environmental Transport Association set the initial annual Car-Free Day on the first Tuesday in their Green Transport Week (around 17 June). In 2000 it was agreed to make it a self-standing day held on September 22, originally as a pan-European day organised under the auspices of the European Commission and later with international extensions—during which a large number of cities around the world are invited to close their centers to cars. Pedestrians, bicycles, public transit and other forms of sustainable transportation are encouraged on these days. People can reflect on what their city would look like with a lot fewer cars, and what might be needed to make this happen. Advocates claim that over 100 million people in 1,500 cities celebrate International Car-Free Day, though on days and in ways of their choice. This claim, however, is not confirmed.