Ans. Equinoxes and solstices are important markers in the Earth's revolution around the Sun. Equinoxes occur when day and night are approximately equal in length, occurring around March 21 and September 23. Solstices occur when the Sun is at its highest or lowest point in the sky, leading to the longest day (around June 21) and the longest night (around December 21) of the year. These events are crucial for understanding seasonal changes.