field day

Some postulate the idiomatic usage is derived from the "parade day" military use. A parade is much easier than the soldiers’ usual drilling and intense exercise.

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field day (plural field days)

1. (military) A day for manoeuvres and tactical exercises in "the field".
   • 1937, Siegfried Sassoon, Sherston's Progress, London: Faber, page 621 (in The Complete Memoirs of George Sherston ):

     This morning I got up, with great difficulty, at 6.30, and at 7.45 we started out for a Brigade Field Day. Did an attack from 10.30 to 2.30, but it wasn't a strenuous one for me as I was told to "become a casualty" soon after the 3000 yard assault began ….

2. A school day for athletic events; a sports day.
3. A day of class taken away from school for a field trip.
4. (idiomatic) A great time or a great deal to do; a period of bustling activity.

   They went to the park and had a field day playing on the swings.

   • 2014, Vance Munraff, Sounds Like Paradise: a Fugitive's Tale, Lulu.com, →ISBN, page 62:

     A family of frisky squirrels was having a field day amongst the towering obstacle course of foliage.

5. (idiomatic) A great time or a great deal to do, at somebody else's expense.

   The reporters will have a field day with a comment like that.

   The scandal was a field day for the press.

   • 1966 December, Stephen Stills, “For What It's Worth”‎performed by Buffalo Springfield:

     What a field day for the heat (Ooo-ooo-ooo) / A thousand people in the street (Ooo-ooo-ooo) / Singing songs and a-carryin' signs (Ooo-ooo-ooo) / Mostly say "Hooray for our side" (Ooo-ooo-ooo)

   • 2009, Julie Jurgens-Shimek, Autism Is a Four Letter Word: Love, AuthorHouse, →ISBN, page 32:

     It had become a legal nightmare. All parties had retained attorneys; the community and press were having a field day.

   • 2012, Claudia Parker, Becoming a Mother, While Losing My Own, Xlibris Corporation, →ISBN, page 158:

     I thought I'd been so thorough, so efficient, and so cost conscious, but look where I was now. The devil was having a field day with my head.

   • 2012, Gary Rosen, Unfair to Genius: The Strange and Litigious Career of Ira B. Arnstein, Oxford University Press, →ISBN, page 140:

     The reporters were having a field day with our saga and the courtroom filled with spectators.

   • 2022 November 15, Patrick Wintour, “Sergei Lavrov, a fixture of Russian diplomacy facing his toughest test in Ukraine”, in The Guardian‎:

     The Russian foreign ministry had a field day denouncing what it called western propaganda as a high-level lie.

6. (US military, specifically US Navy, US Coast Guard and US Marine Corps) A day on which there is top-to-bottom all-hands cleaning.

• open field (idiomatic)

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