I disagree most vehemently with the concept of Tau day. First, I am too old to learn new math. Second, Pi makes sense to the elders. Consider a hat maker or brassiere seamstress. How do they set the diameter of a hat or bra? They take a tape measure and wrap it around the object of interest. With a single factor (1/Pi), they take that circumference and turn it into a diameter. Of course, I am so learned that I can just look at/feel a breast and tell you the correct cup size.

(It is a complex process, involving volumetric estimation, and my sensitive hand). Lastly, why give up another Greek letter for a constant that is already been spoken for? I want to reserve Tau for a constant of nature that I may discover, such as the perfect shape of a breast (in 3D), or the dimension of the universe.