If you've ever slipped on a shirt that belongs to the opposite sex, you may have paused while trying to button it. For women, the buttons on a shirt are on the left, while for men, they are on the right. Look back to an earlier era to find the reason for the difference.
Back in the Day
Traditionally, men have always dressed themselves. From the perspective of the wearer, buttons on the right side make sense for the vast majority of people who are right-handed. Women once were dressed by handmaids. Buttons were sewn on the left so the dresser -- who probably was right-handed -- could more easily fasten the garment while facing her mistress.