Most people have no idea that Massachusetts license plates are actually hiding a secret code.

The next time you check out your license plate, pay attention to the final number the plate. It turns out that the last number on almost all Massachusetts plates corresponds to the month in which the car’s registration expires!

Flickr/Chris Devers For example, a plate that reads “3H2 BX8” means that the plates expire in August. You can check this against the sticker in the upper left corner, which would read AUG in this case.

So why does this system exist? There’s actually a pretty brilliant reason. It’s an easy way for police officers to check if a car’s registration is expired from a distance. It would be pretty hard to read a registration sticker unless you’re right next to the vehicle, but Massachusetts officers can simply glance at the last number on a license plate (and the color of the sticker on the plate) to tell if someone is driving a car with an expired registration.

Flickr/Jimmy Emmerson

What if a plate ends in 0? That means it expires in October. Another fun fact is that only Massachusetts vanity plates expire in November, and all motorcycle and commercial plates expire on December 31.

Flickr/Chris Devers

For example, a plate that reads “3H2 BX8” means that the plates expire in August. You can check this against the sticker in the upper left corner, which would read AUG in this case.

So why does this system exist? There’s actually a pretty brilliant reason. It’s an easy way for police officers to check if a car’s registration is expired from a distance. It would be pretty hard to read a registration sticker unless you’re right next to the vehicle, but Massachusetts officers can simply glance at the last number on a license plate (and the color of the sticker on the plate) to tell if someone is driving a car with an expired registration.

Flickr/Jimmy Emmerson

It’s a pretty genius system, and Massachusetts is the only state to have implemented it so far. West Virginia and Missouri have similar systems, but they’re based on letter codes and aren’t really as intuitive.

For more of the coolest things Massachusetts has done first, check out this fascinating list.

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