Expressing earliness with "jiu"

Just as 才 can express lateness, 就 can be used to indicate that something happened earlier than expected. The structure is:

Subject + Time + 就 + Verb + Object

In English this might be expressed with "as early as", but usually it's not specifically marked.

Some examples:

• 我们 早上 九点 上课，可是 他 八点 就 来了。
• 她 十八 岁 就 大学 毕业 了。
• 我们 上次 出去 玩，他 九点 就 回去 了。
• 我 五 点 钟 就 到 了 饭馆，你 让 我 等 这么 久，罚 你 请客！

From the example sentences it is clear that 了 naturally occurs with a verb used after 就. This is because verbs following 就 generally have the feeling of being completed.

Sources and further reading

Websites

• East Asia Student: 就 and 才 in Mandarin: as early as, not until