Course deadlines are a way of specifying when and how long a course runs for, as well as how long the course is valid for. To edit course deadlines, click on Teaching then Courses. Click on the course that you want to edit.
Click on the General Settings tab. From there, scroll down to the Course Length and Course Certificate sections. You will see several different options.
Course Length in Days: The Course Length determines how long a learner has to complete a course before they automatically fail it. For example, if your company requires specific training done within 5 days, you would enter 5 in the field. The course length has no effect on the course until the user starts a course -- once they start the course, the timer will start.
Validity Length in Days: The Validity Length determines how long a course is valid for, and upon expiration, will re-enroll previous users. For example, if you have annual safety certification requirements, you could set the Validity Length as 335. This means that 335 days after a user has finished the course, they will be automatically enrolled again and will have 30 days to complete the course before the year is over.
Start Date: The start date determines the earliest calendar day and time (based on the platform time zone) that learners can start the course.
End Date: The end date determines the last calendar day and time (also based on the platform time zone) that learners will have access to the course.
These parameters are applied to every newly enrolled user and they will not apply to users who enrolled before the times were set. To see how to apply deadlines to existing users, as well as how to override deadlines, please see this article.