What is the main difference between 的时候 and 当…时?

The main difference is register and structure. 的时候 is colloquial and attaches to the end of a clause, while 当…时 is formal/literary and brackets the clause. Use 的时候 for everyday speech, and 当…时 for writing or formal speeches.

Can I use 当…时 in everyday conversation?

You can, but it often sounds overly formal or archaic. In casual conversation, native speakers almost always use 的时候. Only use 当…时 if you want to sound literary or emphatic.

When do I use 的时候 vs 当…时?

Use 的时候 for general 'when' statements in both spoken and informal written contexts. Use 当…时 when writing a formal essay, report, or speech, or when you want to emphasize the exact time point of an event.

Can 的时候 and 当…时 be used interchangeably?

Semantically they overlap, but they are not interchangeable due to register and structure. In formal writing, 的时候 may be acceptable but less elegant than 当…时. In speech, 当…时 sounds out of place. Always consider the context.

Easily confusedHSK 4

的时候 vs 当…时 (de shíhou vs dāng…shí): formal vs colloquial 'when'

的时候 and 当…时 both mean 'when' or 'while', but they differ in register and structure. 的时候 is the everyday spoken and written form, placed after a clause or time expression. 当…时 is a more formal, literary pattern that brackets the clause, often used in writing, speeches, or to add emphasis. For casual conversation, use 的时候; for formal or emphatic contexts, use 当…时.

Both 的时候 and 当…时 express 'when' or 'while' in Chinese, but they belong to different registers and have different syntactic structures. 的时候 is the default choice in spoken Mandarin and informal writing: it attaches to the end of a clause or a time noun (e.g., 我吃饭的时候). 当…时 is a more formal and emphatic pattern that brackets the clause (当 + clause + 时), typically found in literary works, speeches, and official writing. While they overlap semantically, 当…时 cannot be used with bare time nouns (e.g., *当2010年时 is unnatural), and 的时候 may sound too casual in very formal contexts where a more elevated tone is expected.

When to use each

的时候de shíhou

when; while

Use 的时候 in everyday conversation and informal writing to indicate the time when an action occurs or a state exists. It attaches directly to the end of a clause (e.g., 你来的时候) or to a specific time noun (e.g., 2010年的时候). It is the most natural and common way to express 'when' in spoken Chinese.

的时候 can also be used with a noun alone, like 吃饭的时候 (at mealtime), whereas 当…时 cannot take a bare noun phrase.

当…时dāng…shí

at the time when

Use 当…时 in formal writing, speeches, or literary works to express a temporal clause with emphasis on the time point. The clause is placed between 当 and 时: 当 + subject + predicate + 时. This pattern signals a more elevated register and is rarely used in casual conversation.

当 may be omitted in some fixed expressions (e.g., 当时 'at that time'), but when used, 当 adds a sense of 'exactly at that moment' and often appears in complex sentences.

At a glance

	的时候	当…时
Register	Colloquial / neutral	Formal / literary
Structure	Post-positioned (clause + 的时候)	Bracketing (当 + clause + 时)
Use with time nouns	Allowed (e.g., 2010年的时候)	Not allowed (*当2010年时)
Emphasis	Neutral time reference	Emphatic or contrasting time point
Frequency in speech	Very common	Rare (sounds stiff)

Examples

的时候
我吃饭的时候看电视。
Wǒ chīfàn de shíhou kàn diànshì.
I watch TV while eating.
Natural everyday usage.
的时候
2010年的时候，我还在上大学。
2010 nián de shíhou, wǒ hái zài shàng dàxué.
In 2010, I was still in college.
的时候 can attach to a specific year.
当…时
当我到达车站时，火车已经开了。
Dāng wǒ dàodá chēzhàn shí, huǒchē yǐjīng kāi le.
When I arrived at the station, the train had already left.
Formal sentence; 当…时 brackets the clause.
当…时
当太阳升起时，我们出发了。
Dāng tàiyáng shēngqǐ shí, wǒmen chūfā le.
When the sun rose, we set off.
Literary or narrative style.
的时候
你来的时候我还在睡觉。
Nǐ lái de shíhou wǒ hái zài shuìjiào.
When you came, I was still sleeping.
Neutral, common in speech.
当…时
当你到达时，请给我打电话。
Dāng nǐ dàodá shí, qǐng gěi wǒ dǎ diànhuà.
When you arrive, please call me.
Slightly formal; in casual speech, 的时候 would be more natural here.

Common mistakes

Using 当…时 in casual conversation, e.g., '当我吃饭时，看电视' sounds stiff and unnatural; use 的时候 instead.
Using 的时候 in very formal writing when a more elevated tone is expected, though it is not incorrect.
Omitting 时 in the 当…时 pattern, e.g., '当我到达，火车开了' is incomplete; 当 must be paired with 时 (or 时候 in some cases, but 时 is standard for this pattern).
Using 当…时 with a bare time noun, e.g., '当2010年时' is ungrammatical; say '2010年的时候'.

FAQ

What is the main difference between 的时候 and 当…时?: The main difference is register and structure. 的时候 is colloquial and attaches to the end of a clause, while 当…时 is formal/literary and brackets the clause. Use 的时候 for everyday speech, and 当…时 for writing or formal speeches.
Can I use 当…时 in everyday conversation?: You can, but it often sounds overly formal or archaic. In casual conversation, native speakers almost always use 的时候. Only use 当…时 if you want to sound literary or emphatic.
When do I use 的时候 vs 当…时?: Use 的时候 for general 'when' statements in both spoken and informal written contexts. Use 当…时 when writing a formal essay, report, or speech, or when you want to emphasize the exact time point of an event.
Can 的时候 and 当…时 be used interchangeably?: Semantically they overlap, but they are not interchangeable due to register and structure. In formal writing, 的时候 may be acceptable but less elegant than 当…时. In speech, 当…时 sounds out of place. Always consider the context.