With sense 3, compare Frenchl'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.
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.
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
1917
The coming of the zero hour of 3.30 in the morning.
W. Beach Thomas, With British on Sommeii. v
1927
Zero hour—the six o'clock shift waits to go on.
New Yorker 22 October 48/2 (caption)
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
1953
Incidentally, zero hour for tax-payments is approaching.
A. Huxley, Letter 2 February (1969) 664
2007
Almost all the elements for terror attacks were complete except for setting the zero hour for the attacks.
The hour from which a new cycle of time is measured; spec. midnight, as the beginning of the day.
1939
Methought..I heard at zero hour as 'twere the peal of vixen's laughter among midnight's chimes.
J. Joyce, Finnegans Wakeiii. 403
1942
The interval between zero hour and noon..called A. M. (ante-meridian).
D. Polowe, Navigation for Mariners & Aviators xii. 152
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.
ELHvol. 26 416
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, Jamaicavol. II. ii. 45
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.
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.
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.