Step day

A date referred to in The Long Earth. It was on this day that the Stepper, a device invented by Willis Linsay, was first made available to the public, via posting the blueprints online. Soon, most youths had built one, and had ended up in one of the Long Earths, nauseous and severely worried. It was only due to the noble efforts of the young Joshua Valiente that they managed to get back to what would eventually be called Datum Earth.