The "use by" date is just that. If senna or any pill, food, or product that has a "use by" date on it is good until that date - no longer at all - PERIOD.
Think of it this way - you buy ½ lb. of deli turkey at your supermarket and it has printed on the label "use by October 7, 2014." Would you eat it on October 15 or October 30, 2014?
All the best,
Search for questions
Still looking for answers? Try searching for what you seek or ask your own question.