Where the Rubber Hits the Road
Check Car Tire Inflation Day is pretty simple to celebrate, at least, on most older cars it is.
To do this yourself, all you need is a pressure gauge, which you probably already have. It was likely passed down to you from your father. Nobody actually goes out to buy one of these things anymore.
That last statement is probably more true than you think.
On newer cars, the computer and built-in sensors check the pressure for you and tell you if it's not right via an idiot light on the dashboard (or perhaps an even more advanced way).
When this is the case, you don't need a pressure gauge. You just need to go to an air pump to fill your tires to the proper amount. It's very unlikely that your tires are over-inflated.
So today is mostly about those older, stupider cars that need their tire pressure checked manually.
Some people purposely over-inflate the tires for better gas mileage but a rougher ride. Other under-inflate them for converse reasons.
Whatever you like to do regarding your car's (or truck's) tires, today is the day to get out there and have at it. Enjoy.