Handling Date & Time in R | Date Arithmetic | R Training | Rsquared Academy

Hello, great to have such a deep dive in dates. My question is: In my mind and diary, when a course starts April 12 and ends April 21, the length of the course lasts 10 days, not 9. Because I would be required to attend on the first day and on the final day. What would be the best strategy to deal with this?