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Can you tell me how I could refer to a day when some people can't drive in a city to avoid making pollution even worse? Some people here call it 'rotation day' since you can't drive on a certain day of the week depending on the last number in your car plate. For example on Mondays cars with plate ending in 1 or 2, on Tuesdays cars with plates ending in 3 or 4, etc...Thanks!