White T-Shirt Day is celebrated on February 11, 2021. It marks the end of a union strike by employees of General Motors in 1937. The Flint Sit-Down Strike against General Motors changed the United Automobile Workers (UAW) from a collection of isolated locals on the fringes of the industry into a major labor union and led to the unionization of the domestic United States automobile industry. White T-Shirt Day is also known as White Shirt Day. The rules to celebrate the day are those: wear a white shirt or blouse, don't let this shirt get dirtier than your boss's shirt, follow work and safety rules as usual.