The baseball season usually begins in the spring and ends in the fall, players often play during the day and games are usually canceled when it rains, meaning players are subject to a lot of sunlight when on the field. There are a lot of methods used by baseball players to avoid the sun and using sunglasses is one of the most common. This is another unofficial part of the uniform. It helps players keep their eye on the ball on sunny days, so that they can make plays. They're often form fitting to the face so they don't fall off. They also typically protect from UV rays to keep a player safe.