Z-day, n.

z-day
http://www.oed.com/dictionary/z-day_n%3Ftab%3Dmeaning_and_use
First published 1986; not fully revised

# Z-daynoun

## Factsheet

### What does the noun Z-day mean?

There is one meaning in OED's entry for the noun Z-day. See ‘Meaning & use’ for definition, usage, and quotation evidence.

#### Entry status

OED is undergoing a continuous programme of revision to modernize and improve definitions. This entry has not yet been fully revised.

### How common is the noun Z-day?

Fewer than 0.01occurrences per million words in modern written English

1920 | 0.002
1930 | 0.0019
1940 | 0.0016
1950 | 0.0014
1960 | 0.0014
1970 | 0.0014
1980 | 0.0008
1990 | 0.0004
2000 | 0.0002
2010 | 0.0001

### Where does the noun Z-day come from?

Earliest known use

1920s

The earliest known use of the noun Z-day is in the 1920s.

OED's earliest evidence for Z-day is from 1925, in a text by Edward Fraser and John Gibbons.

### Nearby entries

1. zawiya, n. 1836–
2. zawn, n. 1865–
3. zayat, n. 1823–
4. zayde, n. 1946–
5. zazen, n. 1727–
6. zazzy, adj. 1961–
7. Z band, n. 1950–
8. ZBB, n. 1976–
9. Z-bed, n. 1973–
10. Z-car, n. 1961–
11. Z-day, n.1925–
12. Z-DNA, n. 1979–
13. ze, pron. 1864–
14. zea, n. 1562–
15. zeagonite, n. 1823–
16. zeal, n. a1382–
17. zeal, v. 1542–1687
18. Zealander, n.¹ 1663–
19. Zealander, n.² 1773–
20. Zealandic, adj. 1807–
21. Zealandish, adj. 1684–

## Meaning & use

Military.

1. 1925–
   = zero day n. 1.
   1. 1925

      > The opening of the main attack of the battle of the Somme was fixed for June 29th, and notified beforehand as ‘Z Day’.

      E. Fraser & J. Gibbons, Soldier & Sailor Words 312
   2. 1930

      > Operation Orders..notified us that Thursday was ‘Z’ (or zero) day.

      S. Sassoon, Memoirs of Infantry Officer iv. 61
   3. 1938

      > In the sour concrete hole the corporal shows his muddy map, his Z Day zone of fire.

      E. Blunden, On Several Occasions
   military
   1. zero 1849–
      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 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…
   3. Z-day 1925–
      = zero day, n. 1.
   View in Historical Thesaurus

## Frequency

Z-day typically occurs fewer than 0.01 times per million words in modern written English.

Z-day is in frequency band 1, which contains words occurring fewer than 0.001 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 Z-day, n., 1920–2010

* 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
--- | ---
1920 | 0.002
1930 | 0.0019
1940 | 0.0016
1950 | 0.0014
1960 | 0.0014
1970 | 0.0014
1980 | 0.0008
1990 | 0.0004
2000 | 0.0002
2010 | 0.0001

Originally published as part of the entry for Z, n.

Z, n. was first published in 1921; not fully revised.