To express a period of time: complement of duration

In Chinese, a Complement of Duration is used to indicate how long an action or state lasts.

Common duration expressions: 一刻钟 (yí kèzhōng — 15 minutes / a quarter), 半个小时 (bàn gè xiǎoshí — half an hour), 两天 (liǎng tiān — two days), 三个月 (sān gè yuè — three months).

1. Duration of a Completed Action

This structure indicates that an action lasted for a specific period of time and has already finished.

2. Duration of an Ongoing Action

Adding a second 了 (le) at the end of the sentence indicates that the action has been going on for a period of time and is still continuing.