A seasonal equinox occurs twice a year when day and night are approximately equal in length. This phenomenon happens around March 20 or 21, marking the start of spring in the Northern Hemisphere, and around September 22 or 23, signaling the beginning of autumn. During these times, the sun is positioned directly above the Equator. The equinoxes are significant in many cultures and are often associated with various festivals and traditions. They also play a crucial role in astronomy and climatology, helping to define the changing seasons and the Earth's tilt in relation to the sun.