Odd–even rationing

Odd–even rationing is a method of rationing in which access to some resource is restricted to some of the population on any given day. In a common example, drivers of private vehicles may be allowed to drive, park, or purchase gasoline on alternating days, according to whether the last digit in their license plate is even or odd. Similarly, during a drought, houses can be restricted from using water outdoors according to the parity of the house number.

Typically a day is "odd" or "even" depending on the day of the month. An issue with this approach is that two "odd" days in a row occur whenever a month ends on an odd-numbered day. Sometimes odd or even may be based on day of the week, with Sundays excluded or included for everyone.