You must TAKE the exam before March 6. It means, that you must REGISTER for the exam few days before you can take it. For EXAMPLE, I need to register 5 days before I can take the exam. So, if I take exam on March 3, I must register before Februar 26. Also test center can have it's own internal problems both with registration and the exam itself. So, CONTACT YOUR LOCAL TEST CENTER to know exact dates for you.