“时期” is a versatile and common noun used across various contexts, from formal academic writing to everyday conversation.
Historical Context: This is its most frequent use. It's almost always attached to a dynasty, event, or historical description. (e.g., 春秋战国时期 - Spring and Autumn and Warring States Period).
Personal Development: Used to describe stages of life. (e.g., 青春期 - qingchūnqī - adolescence/puberty period, 婴儿期 - yīng'érqī - infancy period).
Projects & Processes: Used to define phases of a plan or process. It's often combined with words like “initial,” “middle,” and “late.” (e.g., 项目的初期 - xiàngmù de chūqī - the initial period of the project).
Social & Economic Contexts: Used to describe a time characterized by a specific social or economic state. (e.g., 经济困难时期 - jīngjì kùnnán shíqī - period of economic difficulty).
Formality: Generally neutral to slightly formal. It's more formal than just saying “that time” but is perfectly acceptable in daily speech.