Yes, cardiovascular exercise is cumulative; this means that you could do a short session in the morning and another at night and have the same benefits of a long session in the afternoon.
We all know the health benefits of cardio exercise: it strengthens your heart and lungs, helps you get rid of excess calories and body fat, increases your bone density and improves muscle tone. Not only! It also cheers you up, and doctors have advised cardio exercise to help their patients fight depression.
Cardio include: swimming, biking, running, walking, dancing, plain step aerobics, rowing, rope jumping or playing sports like football, volleyball and tennis.
All you really have to fight is inertia. Once you start, you will get hooked. Regular exercisers know this: shortly after you begin training, your body responds by producing more endorphins and hormones that enhance your mood and stimulates the pleasure centres in the brain. You will feel very good doing the exercises, and your body will want more.