zero hour

zero hour (plural zero hours)

1. Synonym of H-hour.
   • 1929, Sir Arthur Conan Doyle, When the World Screamed‎:

     I waited with occasional glances at my watch until the zero hour should arrive.

   • 1937, Siegfried Sassoon, The Complete Memoirs of George Sherston, London: Faber, page 339 (1972 paperback edition):

     Zero hour was forty-five minutes after midnight. Two companies were to attack on a 600-yard front …

   • 1972 April 17, Elton John, Bernie Taupin, “Rocket Man”, in Honky Château‎, performed by Elton John:

     She packed my bags last night, pre-flight / Zero hour 9 a.m. / And I'm gonna be high / As a kite by then

• D-Day, X-Day
• zero-hour contract