Time Relationships Between Clauses: 的时候, 以前, 以后, 一...就, 当...时

When you want to connect two events in time, whether one happens before the other, at the same moment, or immediately after, Chinese has a set of patterns for exactly that. These are some of the most useful sentence-linking tools you will learn, and several of them appear even at the beginner level.

的时候: "when," during an action or state

的时候 (de shíhou) attaches to a verb or adjective and means "when" or "at the time of." It describes what was happening at the moment something else occurred.

[Verb/Adjective] + 的时候, [Main Clause]

• 我吃饭的时候不看手机。(Wǒ chīfàn de shíhou bù kàn shǒujī.) -- When I eat, I don't look at my phone.
• 她小的时候住在农村。(Tā xiǎo de shíhou zhù zài nóngcūn.) -- When she was young, she lived in the countryside.
• 你离开的时候，请关灯。(Nǐ líkāi de shíhou, qǐng guān dēng.) -- When you leave, please turn off the lights.

的时候 describes an ongoing state or action that forms the backdrop for something else. Think of it as "during the time when X was happening." The two events overlap in time.

以前 and 以后: "before" and "after"

以前 (yǐqián, "before" or "in the past") and 以后 (yǐhòu, "after" or "in the future") attach to a verb phrase to place events in sequence. They work the same way and are worth learning together.

[Verb Phrase] + 以前/以后, [Main Clause]

• 吃饭以前，先洗手。(Chīfàn yǐqián, xiān xǐ shǒu.) -- Before eating, wash your hands first.
• 来中国以前，我没学过汉语。(Lái Zhōngguó yǐqián, wǒ méi xué guò Hànyǔ.) -- Before coming to China, I had never studied Chinese.
• 下课以后，我们去喝咖啡。(Xià kè yǐhòu, wǒmen qù hē kāfēi.) -- After class, let's go get coffee.
• 毕业以后，他去了上海工作。(Bìyè yǐhòu, tā qù le Shànghǎi gōngzuò.) -- After graduating, he went to Shanghai to work.

On their own, 以前 and 以后 mean "in the past" and "in the future" respectively. Attached to a verb phrase, they become "before doing X" and "after doing X." Both uses are common and learners pick up the difference quickly from context.

一...就: "as soon as... then"

一...就 (yī...jiù) links two events that happen in immediate sequence. The moment the first thing happens, the second follows right away. There is no gap.

一 + [First Event] + 就 + [Immediate Result]

• 我一到家就睡着了。(Wǒ yī dào jiā jiù shuìzháo le.) -- As soon as I got home, I fell asleep.
• 她一看到他就笑了。(Tā yī kàn dào tā jiù xiào le.) -- The moment she saw him, she smiled.
• 你一说完，他就离开了。(Nǐ yī shuō wán, tā jiù líkāi le.) -- The moment you finished speaking, he left.
• 天一亮，我们就出发。(Tiān yī liàng, wǒmen jiù chūfā.) -- As soon as it gets light, we'll set off.

一 here is not the number one. It functions as "once" or "the moment that." The two events can share a subject or have different subjects, as the last two examples show. This pattern is very natural in spoken Chinese and comes up constantly.

当...时: "when," more formal

当...时 (dāng...shí) is a more formal version of 的时候. 当 opens the time clause and 时 closes it, with the verb phrase sitting between them.

当 + [Verb Phrase] + 时, [Main Clause]

• 当他进来的时候，大家都安静下来了。(Dāng tā jìnlái de shíhou, dàjiā dōu ānjìng xiàlái le.) -- When he walked in, everyone went quiet.
• 当我遇到困难时，我会想起他的话。(Dāng wǒ yùdào kùnnán shí, wǒ huì xiǎngqǐ tā de huà.) -- When I face difficulties, I think of what he said.
• 当经济快速发展时，新的问题也出现了。(Dāng jīngjì kuàisù fāzhǎn shí, xīn de wèntí yě chūxiàn le.) -- When the economy was developing rapidly, new problems also emerged.

当...时 is mostly a written pattern, common in essays, news articles, and formal speech. In everyday conversation, 的时候 handles the same job more naturally. You will encounter 当...时 often in reading material from the intermediate level onward, so it is worth recognizing even if you do not produce it often yourself.

Note that 当...时 and 当...的时候 are both acceptable. The longer form with 的时候 inside is common and not redundant.

How they compare

Pattern	Meaning	Feel	Position
的时候	When, during	Everyday	Attached to verb before main clause
以前	Before doing X	Everyday	Attached to verb before main clause
以后	After doing X	Everyday	Attached to verb before main clause
一...就	As soon as, the moment	Everyday	Spans the two clauses
当...时	When, at the time of	Formal / written	Wraps around the verb

All five patterns appear regularly in Chinese, and the everyday ones (的时候, 以前, 以后, 一...就) are worth getting solid early. They come up from the beginner level and keep paying off at every stage.