The increase in daylight during spring happens because the Earth's axis is tilted about 23.5 degrees relative to its orbit around the Sun. This tilt causes different parts of the Earth to receive varying amounts of sunlight throughout the year. During spring, the hemisphere tilted towards the Sun begins to receive more direct sunlight, making days longer. The rate of daylight increase peaks around the spring equinox when the tilt causes the number of daylight hours to grow fastest, moving from the shorter days of winter towards the longer days of summer. In summary, daylight increases in spring because Earth's tilted axis causes the hemisphere to gradually tilt more towards the Sun as it revolves around it, lengthening the hours of sunlight each day until the summer solstice.