For centuries, people have watched the sky for the changes of season and then celebrated with colorful festivals and rituals.
In India, many people celebrate the festival of Navroze, or "new Day," on the spring equinox. It is a day to clean and paint houses, wear new clothes, and hang jasmine flowers and roses on doors and windows.
In ancient times, women and girls in Sweden would bathe in a river in the belief that this would bring plenty of rain for the crops, while village people would dance around a decorated tree.
Now, in late June, Swedes dance around a pole covered with greenery and flowers.
The Chinese mark the end of summer with the Mid-Autumn Moon Festival, which occurs when the Moon is at its brightest.
After dark, people stroll with brightly lit lanterns, admire the full Moon, and eat moon cakes, which are pastries with a whole egg yolk in the center symbolizing the Moon.
Ancient Romans welcomed winter with the festival of Saturnalia, honoring Saturn, the god of agriculture. People decorated their houses with evergreen branches and lit lamps all night to ward off the darkness.