Do you mean a certain time of the day or do you mean a certain condition? If you are asking about a condition, it can help in case of constipation, cold, flu and pain relief. The dosage and its time can vary.
Depends what you want from it. If it’s just to boost the immune system a teaspoon a day is enough. If you are taking it for a cold or flu, start the dosage at the first sign of trouble. 4 tsps a day are more than enough.