period in advance

例句：

1. 1. The teacher explained the concept of time in periods.
   老师在课程中讲解了时间的概念。
2. 2. During the summer vacation, students have different periods of rest and study.
   暑假期间，学生们有不同的休息和学习周期。
3. 3. The project has a 10-year period of implementation.
   该项目有10年的执行周期。