Order of posts on homepage

I have set the various sections of the homepage (i.e. news, features, courses) to show posts from a specific category. However, it is showing the oldest posts, not the latest posts. This results in the homepage showing the oldest news only, and it doesn't change when new posts are published. How can I change this so the latest news is shown? I've tried deactivating all my plugins and clearing caches but it persists. Thanks.