To edit or delete a year or semester, go to the Years page and then click on the name of the year or semester you want to edit or delete.
To find the Years page, on Android, open the top left hamburger menu. On iOS, open the bottom right tab and select View years/semesters. On Windows, use the side menu.
Then you can edit the semester or year however you'd like!
To delete the semester/year, click the delete icon in the top right (on some platforms, this might be hidden in the "..." menu).