There are four special occasions during a year — two equinoxes and two solstices — that have astronomical significance and they mark the beginning of the four seasons. But they also have cultural significance among certain people and cultures of the world such as Persians.
An equinox occurs when the length of the day and night is equal. More technically, the tilt of the earth with respect to sun is at its minimum at an equinox. Vernal equinox occurs on March 20 or 21, and it marks the beginning of Spring in the northern hemisphere of earth and the beginning of Fall in the southern hemisphere. More >