Bharatnatyam is structured according to the examinations conducted by the University. It typically takes about 6-7 years to complete the examinations. You can learn it for fun as well without actually wanting to go through exams. It has immense health benefits and good cardio workout. Bollywood, on the other hand, is energetic and fun-filled and can be learnt one song at a time. I usually assess the ability of the student to grasp the movements and teach accordingly. It can take anywhere between 2 weeks to 4 months to learn a complete Bollywood dance item.