If you're SURE that those dates are correct, it seems obvious that you should prioritise those parts of the course which will be assessed first. (The only exception would be if you're studying a hierarchical subject, such as Mathematics, where you have to study parts of the course in a particular order, as one component builds upon another).
If in doubt about, you can find the relevant dates (for all A level courses, irrespective of the subject or examining body) here:
http://www.modernisat...org.uk/comptimetable/
Chris