zero-dayhttp://www.oed.com/dictionary/zero-day_n%3Ftab%3Dmeaning_and_usezero day, n.
Revised 2018

zero daynoun

  1. 1.
    1917–
    Military. The day on which a military operation is scheduled to begin. Also in extended use: the day on which any significant event or activity is scheduled to begin or take place. Cf. zero hour n. 1.
    1. 1917
      The assault, which will be preceded by a five days' artillery bombardment, will take place about dawn on Zero day.
      Attack Brit. 9th Corps Messines Ridge (U.S. War Dept. Doc. No. 653) 12
    2. 1947
      I..fixed a zero-day three months ahead.
      L. Hastings, Dragons are Extra iv. 80
    3. 1952
      Stilfontein's zero day is Tuesday next, when the mine will officially be producing gold.
      Financial Times 30 June 3/2
    4. 1978
      20th October had been fixed as Zero Day for rocket attacks on London to begin.
      R. V. Jones, Most Secret War xxxix. 350
    5. 2007
      Working parties had filled in shell craters and bridged trenches in order to have roads built as far as the front line by zero day.
      P. D. Dickson, Thoroughly Canadian General iii. 53
  2. 2.
    Computing.
    1. 2.a.
      1993–
      attributive. Designating (an item of) commercial software, media, etc., illegally made available via the internet on the same day as (or sometimes earlier than) its official release. Chiefly in zero day warez (see warez n.).
      1. [1992
        The target for all these groups was ‘zero wares’, software that had been cracked less than 24 hours earlier—zero days.
        Sydney Morning Herald (Nexis) 28 September 18]
      2. 1993
        There was talk in this group about zero day warez.
        Goal! Piracy in comp.sys.amiga.advocacy 28 June (Usenet newsgroup, accessed 11 Jan. 2018)
      3. 2004
        Zero Day cracks appear even before the products have been released.
        What Crap is This? in comp.os.linux.advocacy (Usenet newsgroup, accessed 11 Jan. 2018) 24 July
      4. 2017
        Oh that kind of pirate. I was going to bring up BitTorrent and zero day warez.
        @MCWronski 19 September in twitter.com (accessed 11 Jan. 2018)
    2. 2.b.
      2000–
      attributive. Designating a software vulnerability that is unknown to the developer or vendor, making it vulnerable to an attack until it is discovered and fixed; designating an attack or method of attack which exploits such a vulnerability.
      1. 2000
        The so-called zero day exploit list..features a minimum of 100 fresh vulnerabilities a week.
        ‘We're the Good Guys’ claim Hackers in alt.hit2000.nl 14 April (Usenet newsgroup, accessed 11 Jan. 2018)
      2. 2006
        The attacks..use phishing e-mails to get employees to open e-mail attachments or visit Web sites that download Trojans targeting ‘zero-day’ vulnerabilities in common apps.
        InfoWorld 30 October 26/1
      3. 2017
        The breach could be the result of a so-called zero-day attack, one that exploits a flaw in software not identified or patched by the supplier.
        Times (Nexis) 16 June 16

Originally published as part of the entry for zero, n. & adj.

zero day, n. was revised in June 2018.

zero day, n. was last modified in December 2023.