To edit the date of a particular class or to delete a class from a course, return back to the register of players page and select 'view classes'.
This will bring up a list of the classes for that course, click onto the one you wish to edit.
Here you can edit the session details, such as the date and time. Once you have done this save the class. If you wish to cancel a class due to bad weather or half term for example you can also do that here by selecting 'cancel class'. This won't effect the other upcoming classes.