zero hour, n.

zero-hour
http://www.oed.com/dictionary/zero-hour_n%3Ftab%3Dmeaning_and_use
Revised 2014

# zero hournoun

## Factsheet

### What does the noun zero hour mean?

There are three meanings listed in OED's entry for the noun zero hour. See ‘Meaning & use’ for definitions, usage, and quotation evidence.

### How common is the noun zero hour?

About 0.1occurrences per million words in modern written English

1910 | 0.2
1920 | 0.19
1930 | 0.18
1940 | 0.17
1950 | 0.18
1960 | 0.16
1970 | 0.14
1980 | 0.11
1990 | 0.097
2000 | 0.088
2010 | 0.083

### How is the noun zero hour pronounced?

#### British English

/ˈzɪərəʊ ˌaʊə/
ZEER-oh ow-uh

#### U.S. English

/ˈzɪroʊ ˌaʊ(ə)r/
ZEER-oh ow-uhr
/ˈziroʊ ˌaʊ(ə)r/
ZEER-oh ow-uhr

### Where does the noun zero hour come from?

Earliest known use

1910s

The earliest known use of the noun zero hour is in the 1910s.

OED's earliest evidence for zero hour is from 1915, in New York Times.

zero hour is formed within English, by compounding.

Etymons: zero n., hour n.

### Nearby entries

1. zero-emission, n. & adj. 1952–
2. zero-energy, adj. 1947–
3. zero-field, adj. 1915–
4. zero-G, adj. & n. 1950–
5. zero grade, n. 1888–
6. zero gravity, n. & adj. 1915–
7. zero-graze, v. 1954–
8. zero-grazed, adj. 1958–
9. zero grazing, n. 1954–
10. zero growth, n. 1907–
11. zero hour, n.1915–
12. zero-hours, adj. 1988–
13. zeroing, n. 1906–
14. zeroize, v. 1894–
15. zero-length, adj. 1945–
16. zero-line, n. 1834–
17. zero magnet, n. 1890–
18. zero mark, n. 1821–
19. zero meridian, n. 1849–
20. zero norm, n. 1966–
21. zero option, n. 1976–

## Etymology

### Summary

Formed within English, by compounding.
< zero n. + hour n.…
< zero n. + hour n.

### Notes

With sense 3, compare French l'heure zéro (1848 or earlier denoting the hour from which a period of time is measured), zéro heure (1857 or earlier denoting midnight).

## Meaning & use

1. 1.
   1915–
   The time at which a military operation is scheduled to begin. Also in extended use: the time at which any (typically significant) event is scheduled to take place.
   1. 1915

      > At 5:05 A. M. Sept. 25 a message came to the dugout that the ‘zero’ hour, that is, the time the gas was to be started, would be at 5:50 A. M.

      New York Times 9 November 2/3
   2. 1917

      > The coming of the zero hour of 3.30 in the morning.

      W. Beach Thomas, With British on Somme ii. v
   3. 1927

      > Zero hour—the six o'clock shift waits to go on.

      New Yorker 22 October 48/2 (caption)
   4. 1939

      > Your duties will not begin till after dinner. Zero hour is at nine-thirty sharp.

      P. G. Wodehouse, Uncle Fred in Springtime xviii. 269
   5. 1953

      > Incidentally, zero hour for tax-payments is approaching.

      A. Huxley, Letter 2 February (1969) 664
   6. 2007

      > Almost all the elements for terror attacks were complete except for setting the zero hour for the attacks.

      Washington Post (Nexis) 28 April a12
   military
   1. hour of zero 1915–
      The initial point of a process or sequence of events; the starting point, the absolute beginning; (Military) the time or day when an attack or…
   2. zero hour 1915–
      The time at which a military operation is scheduled to begin. Also in extended use: the time at which any (typically significant) event is…
   3. jump-off 1918–
      The start of a military operation or campaign. U.S. slang.
   View in Historical Thesaurus
   1. release date 1904–
      The date on which something is released; (now esp.) a date fixed in advance for the release (release, n. II.8) of a film, recording, or similar…
   2. effective date 1909–
      The date on which an order, ruling, appointment, etc., takes effect.
   3. zero hour 1915–
      The time at which a military operation is scheduled to begin. Also in extended use: the time at which any (typically significant) event is…
   4. zero day 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…
   5. start date 1920–
      The date on which something (esp. a job) commences or begins; starting date.
   6. countdown 1953–
      The action of counting in reverse, from a given number to zero, usually in seconds, to mark the lapse of time before an explosion, the launching of…
   7. T 1959–
      Used as a symbol. Astronautics. T represents the time at which a spacecraft is due to be launched.
   View in Historical Thesaurus
2. 2.
   1930–
   The time at which a person feels at his or her lowest. Cf. zero n. A.2.
   Apparently an isolated use.
   1. 1930

      > Psychologists have fixed 11 a.m. as the zero hour of the worker.

      Daily Express 23 May 1/6
   1. zero hour 1930–
      The time at which a person feels at his or her lowest. Cf. zero, n. A.2.
   View in Historical Thesaurus
   1. zero hour 1930–
      The time at which a person feels at his or her lowest. Cf. zero, n. A.2.
   View in Historical Thesaurus
3. 3.
   1939–
   The hour from which a new cycle of time is measured; spec. midnight, as the beginning of the day.
   1. 1939

      > Methought..I heard at zero hour as 'twere the peal of vixen's laughter among midnight's chimes.

      J. Joyce, Finnegans Wake iii. 403
   2. 1942

      > The interval between zero hour and noon..called A. M. (ante-meridian).

      D. Polowe, Navigation for Mariners & Aviators xii. 152
   3. 1959

      > Dickinson habitually passed over the conventional middle of the night as the zero hour, when villages are asleep and unaware of time, preferring midday as the hour when eternity begins.

      ELH vol. 26 416
   4. 2007

      > The ten second count-down began and got louder and louder as it approached zero hour. On the stroke of midnight loud cheers erupted.

      C. Beckford-Brady, Sweet Home, Jamaica vol. II. ii. 45
   1. zero hour 1939–
      The hour from which a new cycle of time is measured; spec. midnight, as the beginning of the day.
   View in Historical Thesaurus
   1. middle night Old English–
      The middle of the night; midnight.
   2. midnight Old English–
      The middle of the night; spec. (now the usual sense) 12 o'clock at night.
   3. noontide 1568–1847
      In extended use: the middle of the night; (also) the position of the moon at midnight. Cf. noon, n. 4. Obsolete. rare.
   4. noon 1605–
      The time of night corresponding to midday; midnight. Frequently in (the) noon of night. Cf. noontide, n. A.2.
   5. witching hour 1762–
      Usually with the. Midnight, with reference to the belief that witches are active and supernatural occurrences take place at that time. More…
   6. long hour 1807–
      Any of the late hours of the day denoted by large numbers, esp. midnight; cf. small hours, n.
   7. midnight 1813–
      An instance or occurrence of midnight.
   8. midnight-tide 1918–
      Midnight.
   9. zero hour 1939–
      The hour from which a new cycle of time is measured; spec. midnight, as the beginning of the day.
   View in Historical Thesaurus

## Pronunciation

### British English

/ˈzɪərəʊ ˌaʊə/
ZEER-oh ow-uh

### U.S. English

/ˈzɪroʊ ˌaʊ(ə)r/
ZEER-oh ow-uhr
/ˈziroʊ ˌaʊ(ə)r/
ZEER-oh ow-uhr

####

##### Consonants

- ppea
- ttea
- kkey
- bbuy
- ddye
- ɡguy
- tʃchore
- dʒjay
- ffore
- θthaw
- ssore
- ʃshore
- vvee
- ðthee
- zzee
- ʒbeige
- xloch
- hhay
- llay
- ɬrhingyll
- rray
- wway
- jyore
- mmay
- nnay
- ŋsing

Some consonants can take the function of the vowel in unstressed syllables. Where necessary, a syllabic marker diacritic is used, hence /ˈpɛtl/ but /ˈpɛtl̩i/.

##### Vowels

- iːfleece
- ihappy
- ɪkit
- ɛdress
- atrap, bath
- ɑːstart, palm, bath
- ɒlot
- ɔːthought, force
- ʌstrut
- ʊfoot
- uːgoose
- əletter
- əːnurse
- ɪənear
- ɛːsquare
- ʊəcure
- eɪface
- ʌɪpride
- aʊmouth
- əʊgoat
- ɔɪvoice
- ãgratin
- ɒ̃salon
- ᵻ(/ɪ/-/ə/)
- ᵿ(/ʊ/-/ə/)

##### Other symbols

- The symbol ˈ at the beginning of a syllable indicates that that syllable is pronounced with primary stress.
- The symbol ˌ at the beginning of a syllable indicates that that syllable is pronounced with secondary stress.
- Round brackets ( ) in a transcription indicate that the symbol within the brackets is optional.

View the pronunciation model here.

####

##### Consonants

- ppea
- ttea
- kkey
- bbuy
- ddye*
- ɡguy
- tʃchore
- dʒjay
- ffore
- θthaw
- ssore
- ʃshore
- vvee
- ðthee
- zzee
- ʒbeige
- xloch
- hhay
- llay
- rray
- wway
- jyore
- mmay
- nnay
- ŋsing

* /d/ also represents a 'tapped' /t/ as in

Some consonants can take the function of the vowel in unstressed syllables. Where necessary, a syllabic marker diacritic is used, hence /ˈpɛd(ə)l/ but /ˈpɛdl̩i/.

##### Vowels

- ifleece, happy
- ɪkit
- ɛdress
- ætrap, bath
- ɑlot, palm, cloth, thought
- ɑrstart
- ɔcloth, thought
- ɔrnorth, force
- ʊfoot
- ugoose
- əstrut, comma
- ərnurse, letter
- ɪ(ə)rnear
- ɛ(ə)rsquare
- ʊ(ə)rcure
- eɪface
- aɪpride
- aʊmouth
- oʊgoat
- ɔɪvoice
- ɑ̃gratin
- æ̃salon
- ᵻ(/ɪ/-/ə/)
- ᵿ(/ʊ/-/ə/)

##### Other symbols

- The symbol ˈ at the beginning of a syllable indicates that that syllable is pronounced with primary stress.
- The symbol ˌ at the beginning of a syllable indicates that that syllable is pronounced with secondary stress.
- Round brackets ( ) in a transcription indicate that the symbol within the brackets is optional.

View the pronunciation model here.

####

Simple text respell breaks words into syllables, separated by a hyphen. The syllable which carries the primary stress is written in capital letters. This key covers both British and U.S. English Simple Text Respell.

##### Consonants

b, d, f, h, k, l, m, n, p, r, s, t, v, w and z have their standard English values

- gguy
- jjay
- yyore
- chchore
- khloch
- shshore
- ththaw
- dhthee
- zhbeige

##### Vowels

- atrap
- ahpalm
- airsquare
- arstart
- arrcarry (British only)
- awthought
- ayface
- a(ng)gratin
- edress
- eefleece
- eerdeer
- errmerry
- ikit
- ighpride
- irrmirror
- olot (British only)
- ohgoat
- oogoose
- oorcure
- orforce
- orrsorry (British only)
- owmouth
- oyvoice
- o(ng)salon
- ustrut
- uhletter
- urnurse
- urrhurry
- uufoot

## Frequency

zero hour typically occurs about 0.1 times per million words in modern written English.

zero hour is in frequency band 4, which contains words occurring between 0.1 and 1 times per million words in modern written English. More about OED's frequency bands

Frequency data is computed programmatically, and should be regarded as an estimate.

### Frequency of zero hour, n., 1910–2010

* Occurrences per million words in written English

Historical frequency series are derived from Google Books Ngrams (version 2), a data set based on the Google Books corpus of several million books printed in English between 1500 and 2010.

The overall frequency for a given word is calculated by summing frequencies for the main form of the word, any plural or inflected forms, and any major spelling variations.

For sets of homographs (distinct entries that share the same word-form, e.g. mole, n.¹, mole, n.², mole, n.³, etc.), we have estimated the frequency of each homograph entry as a fraction of the total Ngrams frequency for the word-form. This may result in inaccuracies.

Smoothing has been applied to series for lower-frequency words, using a moving-average algorithm. This reduces short-term fluctuations, which may be produced by variability in the content of the Google Books corpus.

Decade | Frequency per million words
--- | ---
1910 | 0.2
1920 | 0.19
1930 | 0.18
1940 | 0.17
1950 | 0.18
1960 | 0.16
1970 | 0.14
1980 | 0.11
1990 | 0.097
2000 | 0.088
2010 | 0.083

### Frequency of zero hour, n., 2017–2024

* Occurrences per million words in written English

Modern frequency series are derived from a corpus of 20 billion words, covering the period from 2017 to the present. The corpus is mainly compiled from online news sources, and covers all major varieties of World English.

Smoothing has been applied to series for lower-frequency words, using a moving-average algorithm. This reduces short-term fluctuations, which may be produced by variability in the content of the corpus.

Period | Frequency per million words
--- | ---
2017 | 0.27
2018 | 0.3
2019 | 0.28
2020 | 0.27
2021 | 0.25
2022 | 0.24
2023 | 0.21
2024 | 0.2

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

zero hour, n. was revised in June 2014.

zero hour, n. was last modified in July 2023.