1 definition by New Nutmegger
This term was used by the British Expeditonary Force in preparing for the Battle of the Somme in 1916. It culminated previous days of artillery bombardment called U,V,W,X,Y days. The actual time of attack was called Zero-Hour. Compare these with D-Day and H-Hour used by American troops late in that conflict, terms which became more widespread during WWII.
"Z Day" is found in numerous historical accounts from the time. For instance, from Guy Chapman's wartime memoir, "A Passionate Prodigality": "We were waiting for Z day. ... Once more Z day was postponed."
by New Nutmegger August 18, 2011