When versus how long: the split that decides everything

There are two kinds of time in a Mandarin sentence, and they live on opposite sides of the verb. Get this split right and the rest of the page is detail.

• Time-WHEN (the point at which something happens) goes BEFORE the verb: 我三点睡 (wǒ sān diǎn shuì) - I sleep at three.
• Time-HOW LONG (the stretch the action lasts) goes AFTER the verb: 我睡了八个小时 (wǒ shuì le bā gè xiǎo shí) - I slept for eight hours.

Both are "time", both can use numbers, and that is exactly why learners mix them up. But they answer different questions. 三点 (sān diǎn) answers when; 八个小时 (bā gè xiǎo shí) answers how long. When-phrases are adverbials and sit in the pre-verb adverbial slot alongside everything else in word order. Duration is a complement, and complements come after the verb. The same noun can do both jobs:

• 他两点上课 (tā liǎng diǎn shàng kè) - he starts class at two (when, before the verb)
• 他上了两个小时的课 (tā shàng le liǎng gè xiǎo shí de kè) - he had two hours of class (how long, after the verb)

For the building blocks of clock times, dates and number-plus-measure phrases, see numbers, time and dates.

The core pattern: verb plus duration

With no object in the way, the pattern is as clean as it gets. Verb, then the duration phrase, with 了 marking that the action happened.

• 他睡了八个小时 (tā shuì le bā gè xiǎo shí) - he slept for eight hours
• 我们走了一个小时 (wǒ men zǒu le yí gè xiǎo shí) - we walked for an hour
• 她哭了半天 (tā kū le bàn tiān) - she cried for ages (半天 literally "half a day", idiomatically "a long while")
• 我等了十分钟 (wǒ děng le shí fēn zhōng) - I waited for ten minutes

The duration phrase is a number plus a duration word: 八个小时 (eight hours), 十分钟 (ten minutes). Note that 小时 (xiǎo shí, hour) takes the measure word 个, so it is 八个小时, while 分钟 (fēn zhōng, minute) and 天 (tiān, day) and 年 (nián, year) are themselves measure-like and take the number directly: 十分钟, 三天, 五年. More on which words need 个 below.

The object problem: repeat the verb or split with 的

The pattern breaks the moment the verb has an object, because the duration wants the slot right after the verb and the object wants it too. They cannot both sit there. Mandarin gives you two ways out, and you should know both.

Option A: repeat the verb

State the verb-plus-object, then say the verb again and hang the duration off the second copy.

• 他学中文学了三年 (tā xué zhōng wén xué le sān nián) - he has studied Chinese for three years
• 我看电视看了两个小时 (wǒ kàn diàn shì kàn le liǎng gè xiǎo shí) - I watched TV for two hours
• 她打电话打了一个小时 (tā dǎ diàn huà dǎ le yí gè xiǎo shí) - she was on the phone for an hour

The first 学中文 sets up what was done; the second 学了三年 carries the tense marker and the duration. This is the verb-copying construction, and it is the safest option in speech because it never sounds wrong.

Option B: duration plus 的 plus object

Put the duration between the verb and the object, joined to the object with 的, exactly as a modifier joins to a noun.

• 他学了三年的中文 (tā xué le sān nián de zhōng wén) - he has studied three years' worth of Chinese
• 我看了两个小时的电视 (wǒ kàn le liǎng gè xiǎo shí de diàn shì) - I watched two hours of TV
• 她打了一个小时的电话 (tā dǎ le yí gè xiǎo shí de diàn huà) - she made an hour's phone call

Here 三年的中文 is literally "three years' worth of Chinese", which is why 的 turns up: the duration is modifying the object just like any other 的 modifier (see the three de). In this pattern the 的 is often dropped in casual speech (他学了三年中文), but writing it is never wrong, so write it.

Both options mean the same thing. The difference is feel: verb-copying foregrounds the activity, the 的 pattern foregrounds the amount. A pronoun object behaves differently again and prefers the verb staying put (我等了他十分钟, "I waited for him ten minutes"), with the duration trailing after the pronoun.

The two 了: finished stretch versus still going

This is where duration complements earn their keep at B2. The placement of 了 tells your listener whether the stretch of time is over or still running.

• 我等了十分钟 (wǒ děng le shí fēn zhōng) - I waited for ten minutes (and then stopped waiting; the wait is over)
• 我等了十分钟了 (wǒ děng le shí fēn zhōng le) - I have been waiting for ten minutes (and I am still waiting now)

One 了 (the verb 了) marks a completed bounded action: the ten minutes happened and finished. Add a second 了 at the very end of the sentence (the sentence-final 了) and you get "ten minutes so far, with the action continuing up to the moment of speaking". The double 了 is the standard way to express the English present-perfect-continuous "have been doing X for Y".

• 他学中文学了三年 (tā xué zhōng wén xué le sān nián) - he studied Chinese for three years (and has finished / stopped)
• 他学中文学了三年了 (tā xué zhōng wén xué le sān nián le) - he has been studying Chinese for three years (and is still at it)

So the rule of thumb: if the speaker is still in the middle of the action, plant the extra 了 at the end. The general behaviour of these two 了 and the other aspect markers is covered in aspect markers; duration is just the place where the contrast is sharpest.

Negation: the duration of NON-action jumps forward

Here is the exception that breaks the after-the-verb rule, and it catches almost everyone. When you say how long something did NOT happen, the duration goes BACK in front of the verb.

• 他三天没吃饭 (tā sān tiān méi chī fàn) - he hasn't eaten for three days
• 我一个星期没见他 (wǒ yí gè xīng qī méi jiàn tā) - I haven't seen him for a week
• 她两年没回家 (tā liǎng nián méi huí jiā) - she hasn't been home for two years

The logic: a non-event has no duration to measure (nothing happened, so there is nothing for the time to be a complement of). Instead the time phrase tells you across what span the non-action held, so it behaves like an adverbial and sits before the verb, in the same slot as a when-phrase. Contrast the positive and negative directly:

• 他吃了三天 (tā chī le sān tiān) - he ate for three days (duration after the verb)
• 他三天没吃 (tā sān tiān méi chī) - he hasn't eaten for three days (duration before the verb)

Same three days, opposite sides of the verb, flipped by 没. If you ever find yourself wanting 没 and a duration in the same clause, the duration goes in front.

Common duration words

The number-plus-duration phrase is built from a fixed set of time words. The one thing to watch is which take the measure word 个 and which do not.

The pattern to internalise: 分钟, 天 and 年 take the number directly, while 小时, 星期/礼拜 and 月 need 个 (and "month as duration" is specifically 个月, not bare 月, since bare 月 with a number means the calendar month: 三月 is March, 三个月 is three months). 星期 and 礼拜 are interchangeable, with 礼拜 the more colloquial. 半天 (literally half a day) and 一会儿 (a little while) are stock vague durations that slot into the same after-the-verb position: 我等了半天 (wǒ děng le bàn tiān), I waited ages; 坐一会儿 (zuò yí huì r), sit for a bit.

The classic learner error

Putting the duration after the object instead of after the verb

This is the single most common duration mistake, straight off the back of English word order. The learner says the verb, says the object, then tacks the duration on the end like an English "for three years". It is wrong.

• ✗ 我学了中文三年 - WRONG. The duration cannot sit after the object 中文.
• 我学中文学了三年 (wǒ xué zhōng wén xué le sān nián) - CORRECT, verb repeated.
• 我学了三年的中文 (wǒ xué le sān nián de zhōng wén) - CORRECT, duration plus 的 before the object.

If a verb has an object, you must use one of the two repair strategies above. There is no version where the bare duration trails the object.

Treating "how long" like "when" and fronting it

The mirror-image slip: knowing that 三点 goes before the verb, the learner fronts the duration too.

• ✗ 他八个小时睡了 - WRONG. This is a duration, not a when, so it cannot sit in front.
• 他睡了八个小时 (tā shuì le bā gè xiǎo shí) - CORRECT, duration after the verb.

Ask which question the time answers. When? goes before the verb. How long? goes after. Only negated non-actions break this, and they break it for a reason.

Forgetting the second 了 for an ongoing action

Learners reliably say 我等了十分钟 when they mean they are still waiting, because the present-perfect-continuous is invisible in the single-了 version.

• 我等了十分钟 - finished waiting. Fine if the wait is over.
• 我等了十分钟了 (wǒ děng le shí fēn zhōng le) - still waiting now. Use this for "I have been waiting ten minutes".

If you are still in the action as you speak, the sentence needs that final 了.

What to drill

1. Ask "when or how long". When goes before the verb (三点睡), how long goes after (睡了八个小时). The question word decides the slot.
2. Never strand a duration after an object. With an object you must repeat the verb (学中文学了三年) or wedge the duration in with 的 (学了三年的中文). 我学了中文三年 is the textbook error.
3. Use the second 了 for "still going". One 了 is a finished stretch (等了十分钟); a final 了 on top means it is still running (等了十分钟了).
4. Flip the duration forward under negation. Non-action duration goes before the verb: 他三天没吃饭, never 他没吃饭三天.
5. Learn which duration words take 个. 小时, 星期, 月 need 个; 分钟, 天, 年 do not. And 三个月 (three months) is not 三月 (March).

For the wider complement system that duration belongs to, see complements. For the 了 and other aspect markers that sit under the finished-versus-ongoing contrast, see aspect markers. For the pre-verb time slot that when-phrases share, see word order and numbers, time and dates.