The length or time span of any drug within the body depends upon a number of factors including those of the physical appearance and the makeup(eg. weight, height, body fat, health issues, etc). Apart from this there might be a number of other factors which might speed up the entire process such as intake of anti-oxidants like juices which help in the removal of the drug from the body in a quick paced manner.
Lastly, the drug has a specific half life time span after which it automatically gets eliminated. Once that is known, the exact days of removal can be easily calculated.