National Odometer Day is May 12th, celebrated by learning a little bit about the odometer, an instrument that indicates the distance traveled by a vehicle.  It may be electronic, mechanical or a combination of both. Odometer comes from the Greek words hodos meaning path or gateway and metron, meaning measure. In some countries, an odometer is called a mileometer, milometer or tripometer. Viewing the dashboard of this vehicle, the odometer is the right side gauge, registering 91,037 miles in the USA!