who knows when

USAGE SUMMARY

The part of a sentence "who knows when" is correct and usable in written English.
You can use it when you want to express uncertainty about the timing of something. For example: No one knows when the recession will end - who knows when things will get back to normal?.

✓ Grammatically correct

News & Media

Wiki

Encyclopedias

Human-verified examples from authoritative sources

Exact Expressions

57 human-written examples

Who knows when it repeats.

The New Yorker

But someday – who knows when?

The Guardian - Tech

"Who knows when Alan's going to retire?

The New York Times

Who knows when they'll come in useful.

The Guardian

Who knows when that mine was laid?

The Guardian

But who knows when that could change?

The Guardian

"But, who knows when they will come back".

The New York Times

Who knows when a lot of photographers get going?

The New Yorker

Who knows when it will come in useful?

The Guardian - Books

Who knows when, or if, Albany will act?

The New York Times

Who knows when – or if – it will ever be repeated?

The Guardian - Sport

Expert writing Tips

Best practice

Use "who knows when" to express genuine uncertainty about the timing of an event, especially when acknowledging that the timing is unpredictable.

Common error

Avoid using "who knows when" in highly formal writing where a more precise or professional tone is expected. Opt for alternatives like "the timing remains uncertain" or "the exact date is yet to be determined".

Linguistic Context

The phrase "who knows when" functions as an interrogative expression, indicating a lack of knowledge or uncertainty about the timing of a future event. Ludwig's examples demonstrate its use in contexts where predicting the exact time is impossible or speculative.

Expression frequency: Very common

Frequent in

News & Media

50%

Wiki

25%

Encyclopedias

10%

Less common in

Science

5%

Formal & Business

5%

Reference

5%

Ludwig's WRAP-UP

In summary, "who knows when" is a common and grammatically sound phrase used to express uncertainty about the timing of future events. As Ludwig AI also confirms, it's perfectly acceptable in written English and is particularly prevalent in news and media, leaning towards informal usage. While versatile, it's best to avoid it in overly formal settings where more precise language is preferred. Remember that alternative phrases like "it's hard to say when" or "the timing is uncertain" can offer a more formal tone when needed.

More alternative expressions

Phrases that express similar concepts, ordered by semantic similarity:

nobody can say when

Emphasizes the lack of knowledge about the timing.

it's hard to say when

Emphasizes the difficulty in predicting the timing.

we can't determine when

Acknowledges the inability to ascertain the timing.

it's difficult to predict when

Highlights the challenge in forecasting the time.

the timing is uncertain

Focuses on the uncertainty of the time something will occur.

it's anyone's guess when

Implies that the timing is completely unknown and speculative.

the date is unknown

Directly states that the specific date or time is not known.

it remains to be seen when

Suggests that the timing is still pending and needs to be observed.

time will tell

Indicates that the timing will be revealed in the future.

the future is unclear

Highlights the lack of clarity about what will happen in the future.

FAQs

How can I use "who knows when" in a sentence?

Use "who knows when" to express uncertainty about a future event's timing, like: "The project might be delayed, "who knows when" it will actually be completed?"

What's a more formal way to say "who knows when"?

In formal contexts, consider using phrases like "the timing is uncertain", "it is difficult to predict when", or "the exact date is yet to be determined" instead of ""who knows when"".

Is "who knows when" appropriate for academic writing?

While grammatically correct, ""who knows when"" might be too informal for academic papers. Use more precise and formal language like "the specific timeframe is currently unknown".

What is the difference between "who knows when" and "when will it happen"?

"Who knows when" implies a greater degree of uncertainty and unpredictability compared to the direct question "when will it happen?", which seeks a specific answer.