Weekly

Courses may be configured with a specific number of weeks. If weeks are used, then Moodle creates a header that auto-calculates the weeks based on the course start date.

By default, all courses are created with 18 weeks, as a semester generally has 18 weeks of study.

If in the School configuration, the school decides to run classes with more or less weeks, then the default setting should be changes by the admins.  This would also mean all the default courses will need to be manually updated, with the number of topics changes, and activities condensed or expanded to fill the number of weeks the school has chosen. see: weeks-in-a-term

Changing the number of weeks is easily done in the course settings page.