In Persian, we say "When the reed blooms" when we want to express that an event:

  1. Never happens. (This is only the opinion of the speaker so it's not a fact)
  2. It's very unlikely to happen.
  3. It's going to take so long to actually happen. (It's so long that you'd be better off giving up expecting it)

    3.1. We also use it when someone is always postponing something they have to do so you never actually see it happen.

For example:

Kyle: When are you going to pay my money back?

Cartman: When the reed blooms.

Now I don't know if I got the plant's name right because there are some other versions like:

In any event, they have mentioned this plant in the idiom because apparently some versions of it actually never bloom. Others believe it's because farmers harvest them before they get the chance to bloom (e.g to make music instruments), so it never happens. I'd love to know the equivalent idioms or expressions for this.

PS: I only know "When pigs fly" but I'm not a fan of it because the word pig sounds a bit rude to me and partly because it implies a strong impossibility which doesn't work for the #3 use.

  • 6
    Does the reed actually bloom on occasion? Because if it doesn't, When pigs fly is very apt. Hell will never freeze over - it is an impossibility if you believe in the traditional hell - so that would equally negate that option. You stated in comments, "...for the idiom in this question, the occurrence of the event even once is very unlikely." You can dislike a reference to pigs, of course, but that doesn't mean it's not a very common (and appropriate) idiom in English. Commented Apr 7, 2016 at 17:30
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    This is confusing. Does it mean all of those things but under different circumstances? Sayings don't often have exact translations that preserve all the nuances.
    – Mitch
    Commented Apr 7, 2016 at 19:05
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    @Sobhan so what is the single thing you want? An English idiom for 'never gonna happen'? For 'very unlikely to happen'? For a single idiom that can be used for both?
    – Mitch
    Commented Apr 7, 2016 at 20:25
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    @Mitch, The idiom I refereed to is used in both scenarios so If there is one that can serve both, it would be awesome. Judging from the answers, English idioms have a distinct line between "never (one's opinion)" and "very unlikely". So if I have to choose I'd like an idiom that conveys "very very very unlikely". As a sidenote, #3.1 is also used commonly so if there is a separate idiom for that, I'd love to hear it.
    – Sobhan
    Commented Apr 7, 2016 at 20:55
  • 4
    @Sobhan - There's a certain ambiguity in idioms - they are idioms, after all - that you're not accepting, but which is no different (apparently) from those in your own language. "When/until the cows come home" is very good. It can mean never, or, since it's not impossible that the cows will come home, rarely. You've stated in comments and updates that you want precise idioms, but you express shifting expectations after they are offered. This site is a question and answer site, not a discussion forum. Maybe what you want is a discussion about idioms? Commented Apr 7, 2016 at 21:53

15 Answers 15


You could say when the cows come home.

Also stated as until the cows come home:

The phrase is often used to describe activities regarded as futile or unproductive.

See also:

Here's another source:

for a very long time

You can diet until the cows come home, and you still won't be a size 4.

We could talk about this problem until the cows come home, but it wouldn't solve anything.

  • 7
    Funny. I always thought the cows would actually be coming home in while. The beef cattle are probably never coming home (assuming they are being driven to the slaughterhouse), but the cows might if they actually want to be milked after being out in the pasture all day. Or at least that's how I always saw it. Commented Apr 7, 2016 at 21:59
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    It's a common idiom in the US, but it has a different meaning from the OP's expression. It really just means "until late tonight".
    – Hot Licks
    Commented Apr 7, 2016 at 23:12
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    @HotLicks That's not the meaning I've heard. "Until the cows come home" means an indefinitely long time. It definitely doesn't mean later tonight, since the cows might never come home! Then again, maybe this is a regional thing. Maybe cows where you're from are more punctual than cows where I'm from. Commented Apr 7, 2016 at 23:17
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    Well, many of the people who used the expression when I was younger actually had experience with cows. They're actually quite punctual.
    – Hot Licks
    Commented Apr 7, 2016 at 23:27
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    It's important to understand that the cows come home near dusk, which is the effective end of the workday on a farm (especially Amish). If you talk about how to fix the fence until the cows come home then it's not going to get fixed today.
    – Hot Licks
    Commented Apr 7, 2016 at 23:39

When hell freezes over is one option, refering to the assumption that hell is an eternally hot and burning place.

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    +1 I think this is a (marginally) better equivalent than the accepted answer... both of them have similar meanings but this one fits more into the contexts where the original expression would be used.
    – user541686
    Commented Apr 8, 2016 at 6:32
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    @Mehrdad, I liked this one too a lot but the original expression is usually used humorously and the accepted answer had more humor in my opinion. And partly because this suggests a very strong impossibility, that didn't work for the #3 use.
    – Sobhan
    Commented Apr 10, 2016 at 4:50
  • Just one more 6 to go :) Commented Apr 11, 2016 at 13:36
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    One version of this is, "There's a snowball's chance in hell, that this will happen".
    – jamesh
    Commented Apr 14, 2016 at 12:17

When pigs fly is an oldie but goodie.

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    I answered with that one too, but then deleted my answer because OP specifically says that one is undesirable. :-( Commented Apr 7, 2016 at 17:50
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    I know the OP doesn't like this one, but he's wrong: there's nothing rude about it, and it is, hands down, the most common idiomatic expression for something that'll never happen.
    – Marthaª
    Commented Apr 7, 2016 at 23:02
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    @Marthaª you need to take the cultural context into account and what is associated with "pigs" in the Middle East. There it would be rude after all.
    – Stephie
    Commented Apr 8, 2016 at 7:01
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    @NVZ: Martha is my real, actual name. I'm not nearly old enough to be Batman's mom (I'm about the same age as Ben Affleck), and passing off Superman as my kid, even an adopted one, would be a real stretch. And I still haven't scraped the time together to see the danged movie.
    – Marthaª
    Commented Apr 8, 2016 at 14:17
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    Didn't the OP as for an English language equivalent to when the Reed blooms, so even though there's cultural differences, it is still a valid answer!
    – RemarkLima
    Commented Apr 9, 2016 at 8:28

One suggestion for this is "Don't hold your breath". Meaning even if something may eventually happen, it is not likely to happen any time soon.


Once in a blue moon expresses a similar sentiment.

To do something “once in a blue moon” is to do it very rarely: “That company puts on a good performance only once in a blue moon.” The phrase refers to the appearance of a second full moon within a calendar month, which actually happens about every thirty-two months. dictionary.com

  • I see, but doesn't it imply that it happens but it's very rarely? Whereas for the idiom in this question, the occurrence of the event even once is very unlikely.
    – Sobhan
    Commented Apr 7, 2016 at 17:04
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    The literal meaning doesn't really carry into its typical usage. Once in a blue moon mostly carries the idea of rarity in a similar way to your 3-part description.
    – Lawrence
    Commented Apr 7, 2016 at 17:08
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    I don't think once in a blue moon depicts unlikeliness, but more that this doesn't happen often (we see blue moons once or twice per year)
    – Chris
    Commented Apr 7, 2016 at 20:02
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    This implies recurrence too.
    – biziclop
    Commented Apr 11, 2016 at 14:36

In a month of Sundays

From TFD

not in a month of Sundays

if you say that something will not happen in a month of Sundays, you mean that it is not likely to happen

He'll never run the marathon, not in a month of Sundays.

More idioms of improbability on Wikipedia. It has expressions in all languages, including the Persian one you've asked in the question.

  • @Sobhan I don't know, exactly. People make such statements of impossibility all the time.
    – NVZ
    Commented Apr 7, 2016 at 19:02
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    @Sobhan Because there's no such thing as a month of Sundays. Even in impossible circumstances, this is still not going to happen.
    – DCShannon
    Commented Apr 8, 2016 at 2:20
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    I always thought this was taken to mean 30-31 weeks, literally the number of Sundays to fill a month. Commented Apr 8, 2016 at 4:28
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    @punkerplunk Wouldn't it be weird to take such a phrase so precisely, when it is patently not precise and could refer to 28, 29, 30, or 31 weeks? It seems so obvious to me to be a figure of speech and not intended to have this kind of precision. Like the security guard at a museum that told a visitor the dinosaur was 65,000,005 years old--since the guard had started work 5 years before, and at that time, he'd been told the dinosaur was 65,000,000 years old...
    – ErikE
    Commented Apr 8, 2016 at 15:55
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    @punkerplunk I think that's just plain silly!
    – ErikE
    Commented Apr 9, 2016 at 0:55

English has separate idioms for never versus rare/ long time.

For never, you could use the construct "Cartman will pay back Kyle right after << insert impossible event here >>" where the event can be improvised on the spot:

  • right after the sky turns pink
  • right after the Pope converts to Methodism
  • right after you bring me some milk from a bull
  • (things mentioned elsewhere, like pigs fly and hell freezes over)
  • etc.

Beware however, that this would be considered snarky or sarcastic, and may not be suitable in all company.

For rare/ long time, two common sayings are "on the fifth Monday in February" or "once in a Blue Moon." In reality, February has five Mondays about once every 28 years, and Blue Moons happen every two to three years, but in figurative terms convey an unspecified degree of rarity.

  • 8
    "On the fifth Monday in February" is certainly not common. This is the first time I've heard it in my four decades plus.
    – Atario
    Commented Apr 7, 2016 at 22:07

I heard a doctor one time say that a condition was "as rare as lips on a chicken".

  • 6
    Was he from one of the southern states of America? Commented Apr 7, 2016 at 18:49
  • More likely from France, where 'when chickens have teeth' is the saying.
    – Phil Sweet
    Commented Apr 7, 2016 at 23:04
  • He was in Florida but he wasn't from the South. Commented Apr 8, 2016 at 10:08
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    Variant: “as rare as hen’s teeth”
    – Greg Bacon
    Commented Apr 8, 2016 at 18:55


Another answer for never is "on February 30th" (for those that use the Gregorian calendar.)

As for #3.1, I had heard the expression "after re-arranging my sock drawer", referring to the doing of something irrelevant and inconsequential being a higher priority than the task in question.


  • A similar one to 30 February is “second Thursday next week”. Commented Mar 18, 2018 at 10:03

When Burnham Wood comes to Dunsinane --Shakespeare.


Sure he'll help me washing the dishes - when Burnham Wood comes to Dunsinane.

In your dreams!

colloq. (orig. U.S.) Not a chance

Public OED


(slang, New York) There is no hope of it being so, the idea is preposterous; do not waste my time with such notions


  • 17
    That's a very specific reference. It comes from Macbeth, and I've never heard it used in a general context. Commented Apr 7, 2016 at 17:51
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    Also, it should be noted that in Macbeth, Burnham Wood does come to Dunsinane, as the attacking army carries branches to hide their numbers.
    – Will
    Commented Apr 7, 2016 at 19:17
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    I like it. Unfortunately, this is somewhat meaningless without the irony. Burnham Wood does come to Dunsinane, and rather swiftly; within the span of one or two Acts, if I recall. This could be very useful for making an ironic remark in some situation when someone in fact thinks that something is as rare as reeds blooming, but it's obvious to you and other that it's not the case.
    – Kaz
    Commented Apr 8, 2016 at 18:09
  • "Nice repair job there. That should hold till Birnham wood comes to Dunsinane, if not longer." (The repair is shoddy and likely to fall apart in days.)
    – Kaz
    Commented Apr 8, 2016 at 18:29
  • Holy cow, there are like quite a few spellings spellings for that Forrest in the original text. Birnan, Birnane, Byrnan, Byrnam, Byrnane.
    – Kaz
    Commented Apr 8, 2016 at 18:34

When two Sundays come together.This proverb means never.

  • Interestingly, on the traditional Jewish calendar this would happen once a year to keep the day of the week and date of the year in sync. It's possible this originally had a meaning closer to the OP's idiom. That being said, it's probably a localized idiom, as I've never run across it.
    – Morgen
    Commented Apr 10, 2016 at 15:46

Said with the right emphasis, you can simply say

That'll happen tomorrow

The idea being that this will still be the case tomorrow, that it will happen tomorrow. But it's never tomorrow, it's always today.

I wish I had a recording of the appropriate emphasis to share with you. A native English speaking friend of yours could probably reproduce it for you. The emphasis is on the 2nd syllable.

  • Very interesting, I tried it couple of times and I think I get the idea. But I fear someone would take it literally (maybe because of accent). Like it would happen tomorrow for real.
    – Sobhan
    Commented Apr 8, 2016 at 8:59
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    As a native speaker of American English, I don't know if I'd interpret "tomorrow" as "some indefinite time in the future", not matter how the emphasis was placed. But this does remind me of "6 to 8 weeks", which is programmer code for "yeah, we know it needs fixing, but don't hold your breath".
    – Marthaª
    Commented Apr 8, 2016 at 18:22
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    Ironic that mañana, which literally means "tomorrow", is used satirically or sarcastically to mean "'sometime in the unspecified future" — but, of course, it's not English. Commented Apr 10, 2016 at 6:20

Try this supreme Quranic idiom: "When the camel enters the eye of the needle"

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    References, please. I've seen similar in Bible, not sure about Qur'an though.
    – NVZ
    Commented Apr 10, 2016 at 4:08
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    It's called ‘the eye’ of the needle, not "hole", and the proverb refers to the sheer difficulty of task at hand, or its impossibility. of completion. "It is easier for a camel to go through the eye of a needle than for a rich man to enter the kingdom of heaven" (or words to that effect)
    – Mari-Lou A
    Commented Apr 10, 2016 at 8:13
  • @NVZ quran.com/7/40
    – caveman
    Commented Apr 10, 2016 at 14:12
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    @caveman thank you. You should always, as much as possible, include such reference in your answer itself. Especially if it's based on religion.
    – NVZ
    Commented Apr 10, 2016 at 14:23

Definitely "when Hell freezes over" or " a cold day in Hell." In traditional Western thought, Hell is an intolerably hot place, where wrongdoers are sent to suffer eternally.


For #3.1, a common expression is "I'll get to it when I get around to it." That's a circular reference that promises action without actually saying when.

See “get round/around to ” meaning and its origin.

When someone says that to you, make sure you have a round tuit so you can give it to them, saying "Now you have a round tuit."

  • 2
    I have multiple round tuits. Doesn't seem to help. There must be something special about how you acquire said round tuit.
    – Marthaª
    Commented Apr 7, 2016 at 23:03
  • @Marthaª Some take years to pay off their tuition loans for their well-rounded tuits.
    – Kaz
    Commented Apr 8, 2016 at 18:12

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