Many time management systems emphasize how they can help you relieve stress. And time management is a tremendous method of handling stress. But time management by itself is not stress management. Focusing on time is only one part of what to do to relieve stress. But time management is a vital component of any stress management system.
What people call "stress" is actually your reaction to a situation you perceive as threatening. This reaction is also called the "fight or flight" reaction, because your body can think of only two things to do: fight it or run from it. Your body floods itself with adrenaline, hormones, and chemicals designed to all your systems on highest alert. The effects of stress on the body include high blood pressure, digestive problems, muscle cramps, headaches, lack of focus and concentration, and other physical and emotional harm.
There are many excellent time management systems, and many excellent marketers seeking to sell them. They emphasize that managing time will relieve stress. But they have no incentive to point out that time management systems don't relieve the stress in bad relationships or the stress of having your values out of line with your goals. And time management systems may allow you to schedule fitness, but they by themselves cannot reverse the ways that stress affects your overall health.
If you are using your time management system to address your stress problems, then you are actually ahead of most people, who think that ignoring stress will make it go away. Most people try to tack on the areas missing, like a separate fitness program and a separate meditation plan. And this can work for some people. However, if this is what you have to do to build a comprehensive stress management system, you are better off beginning with a comprehensive stress program.
Also, any stress management system that does not address time management will not be very effective. The stress caused by a deadline, or by too many things happening at the same time, can be crushing. Relieving this time crunch won't relieve the stress caused by your boss, your co-workers, or your family. 
Many stress management systems are built around a single theme or component.   Some systems developed from time management systems. Others developed from meditation or from health and nutrition backgrounds. While each of these does address the question of how does stress affect your health, developing from a single component will cause a bias in that direction. These systems will be less effective for stressors that come from a different area.
A comprehensive stress management system will have a time management component. It will also have a component to focus on maintaining your physical health, your concentration, your creative thinking, and other skills. Putting these together with time management skills will give you a complete stress management system. Starting with a comprehensive stress management, with the components selected to work together, will probably give you the maximum ability to handle stress.