Hey!

NDA exam is conducted twice a year and minimum age limit to give exam is 16.5-19.5 years, so as per your date of birth you are not eligible for next 4-5 years. Exam is conducted in two rounds, first one exam which consists of general aptitude test and mathematics and second round is 5 days SSB interview.

By this exam candidates are chosen for army, navy and air force.

For more information you can go through this link

https://competition.careers360.com/exams/nda

Thank you