Celebrated every year on December 23.
A long time ago in 1975 on December 23 the US signed the Metric Conversion Act which declares the metric system “the preferred system of weights and measures for United States trade and commerce”.
However the USA still uses inches, feet and pounds to measure length and weight, leading to mass confusion with pretty much the rest of the world who uses the metric system full time.
They even use Fahrenheit for temperature, while most of the world uses Celsius.
We all love individuality. But when it comes to communication using different units is highly impractical.
We celebrate this day hoping for some day in the future where we no longer have to make fun of the USA using their obscure units in all kind of media.
We might as well measure in bananas because bananas take just as much effort to convert to the metric system and sound just as logical to anyone who used metric system all their lives.