In fact, Dec. 22 was only a few seconds longer, but thanks to the Winter Solstice on Saturday, it begins the welcome march not only to spring, but to longer periods of sunlight. There was eight hours, 34 minutes and 24 seconds of daylight Sunday, two seconds longer than Dec. 21.
Next week, days will be almost two minutes longer and by June 21, we'll be enjoying 15 ½ hours of daylight. That's when the Summer Solstice starts and the cycle begins again.
The effect is caused by the Earth's rotation on its axis, which causes the northern portion of the planet to tilt away from the sun in winter, and toward it in summer. Because the sun tilts further and further away from the northern or southern hemisphere, depending on the season, the days grow longer or shorter.
That's why the north and south poles are completely dark or receive constant sunshine for extended periods in winter and summer.
“Because Earth doesn’t orbit upright, but is instead tilted on its axis by 23 1/2 degrees, Earth’s northern and southern hemispheres trade places in receiving the sun’s light and warmth most directly,” according to information from the website earthsky.org. “The tilt of the Earth – not our distance from the sun – is what causes winter and summer. At the December solstice, the northern hemisphere is leaning most away from the sun for the year.”
At the December solstice, all locations south of the equator have day lengths greater than 12 hours. Meanwhile, all locations north of the equator have day lengths less than 12 hours.