Start & End of Period 🩸

Hi ladies 🙋🏻‍♀️ this might be such a silly question but since the beginning of my ttc journey I have always been confused about one thing. What is considered the last day of ones period? Is it when there is only brown discharge on the pad and when you wipe? Is is when there is nothing on the pad but blood when you wipe? Is it when there is absolutely no sign of blood (dried or otherwise) on pad or when wiping? There are so many answers to this and I’m not sure which one is really the correct one?

HELP lol ((: