National Nothing Day is an "un-event" which is celebrated on January 16, 2019 by doing nothing. It was proposed in 1972 by columnist Harold Pullman Coffin. Its purpose is "to provide Americans with one National day when they can just sit without celebrating, observing or honoring anything."
Nothing is no thing, denoting the absence of something. Nothing is a pronoun associated with nothingness. In nontechnical uses, nothing denotes things lacking importance, interest, value, relevance, or significance. Nothingness is the state of being nothing, the state of nonexistence of anything, or the property of having nothing.
Grammatically, the word "nothing" is an indefinite pronoun, which means that it refers to something. One might argue that "nothing" is a concept, and since concepts are things, the concept of "nothing" itself is a thing. Many philosophers hold that the word "nothing" does not function as a noun, as there is no object to which it refers.
In physics, the word nothing is not used in any technical sense. A region of space is called a vacuum if it does not contain any matter, though it can contain physical fields. In fact, it is practically impossible to construct a region of space that contains no matter or fields, since gravity cannot be blocked and all objects at a non-zero temperature radiate electromagnetically. (With material from: Wikipedia)