This article sets out how to limit intake dates for specific courses  

On a course the intake months can be added, navigate to the Course  menu item:

Click on Courses  and a list of all the courses will display:

Search for the desired Course and open the course:

Click on edit to set the intake months:

Select the Enrollment Start Calendar Months  and click on Save:

This will limit the intake months on the enrollment's course if this is setup on the Course