Smoke and Mirrors Day, sometimes referred to as Festival of Smoke and Mirrors Day, is celebrated on March 29th of each year. The staff at National Whatever Day were unable to discover the origin of Smoke and Mirror Day.
Smoke and mirrors is a metaphor for a deceptive, fraudulent or insubstantial explanation or description. The source of the name is based on magicians’ illusions, where magicians make objects appear or disappear by extending or retracting mirrors amid a confusing burst of smoke. The expression may have a connotation of virtuosity or cleverness in carrying out such a deception.
In the field of computer programming, it is used to describe a program or functionality that does not yet exist, but appears as though it does. This is often done to demonstrate what a resulting project will function/look like after the code is complete — at a trade show, for example.
More generally, “smoke and mirrors” may refer to any sort of presentation by which the audience is intended to be deceived, such as an attempt to fool a prospective client into thinking that one has capabilities necessary to deliver a product in question.