Answer:
2 weeks
Explanation: Sadness or darkmood if persists more that 2 weeks and if it affects day to day life activities and creates difficulty in sleeping or eating orders then it should be taken as a form of depression.
Depression is a major illness in our society these days, feeling sad for a day or two for some reason is justifiable but more than 2 weeks without any obvious reason should be addressed as a mental health issue.
Hence a mental health professional must be seen.
