How can I determine when each of the elements- Wood Fire Earth Metal Water gets activated ?

Hi, I don't know if there is midunderstanding on the Five Elements. In ancient astrology, it is believed that everything consists of the five elements. So, they are used to decribe for foretell people's fortune. People's birthday, hours and minutes can be described in the heavenly stems and earthly branches which belongs to different elements. Then they will not what elements they are short of. They can select proper name or wear special ornaments to make up what they lack.