A "short-day" refers to a period when daylight hours are significantly reduced, typically occurring during the winter months. This phenomenon happens because of the tilt of the Earth's axis, which affects how sunlight reaches different parts of the planet. In regions closer to the poles, the difference in daylight can be more pronounced, leading to shorter days and longer nights. During a short-day, activities that rely on natural light may be limited, prompting people to adjust their schedules. This can also impact various aspects of life, including mood and energy levels, as some individuals may experience seasonal affective disorder (SAD) due to reduced exposure to sunlight.