We always round up to the beginning of the next month. If you register any time in January, for instance, your nine months begins on February 1, which would make your deadline November 1. Of course, you should begin working on your course as soon as you enroll. Your deadline is not based on when you send in your first assignment, but on when you enroll . Nine months is plenty of time to finish your course, but it also goes quickly, especially if there are big gaps between assignments.
Most courses take much longer.
Some courses require you to get a graded assignment back before sending in the next one. To avoid delays, do not exceed the specified number of assignments that may be submitted per week. When you receive your instructor's comments on the first assignment, you can revise your work as needed and send it in. Don't expect to complete a correspondence course in no time at all. Remember also that your instructor has many responsibilities other than responding to your assignments.