While the winter solstice begins on Saturday, the sun has already started setting later in the evening for most of the Northern Hemisphere for over a week.For instance, the sunset for Saturday in Los Angeles is at 4:48 p.m., four minutes later than it was on December 10. The amount of time gained each day varies based on a location's latitude.In January, Bismarck gains 39 minutes of evening sun, while Los Angeles gains a mere 28 minutes.It turns out that as our sunsets get later and will continue to do so until the end of June, sunrise times will also continue to get later until roughly January 1. So for most Americans, the shortest day of the year is indeed December 21, when the solstice actually occurs.RELATED STORY | Farmers' Almanac says this winter will be a long, wet, whirlwind of rapid-fire stormsThe sun will rise today in Los Angeles at 6:55 a.m. By December 31, the sun will come up a full three minutes later at 6:58 a.m. The sun rises on Saturday at 7:16 a.m. in New York, but on December 31, the sun will rise at 7:19 a.m.Why does this happen?It is because Earth's orbit around the sun is not perfectly round, and sometimes we find ourselves a little closer to the sun. The Earth is actually 3 million miles closer to the sun in January than in July. This slight change is enough to alter when the sun sets and rises.Because of Earth's shifting distance from the sun, the time it takes for the sun to reach the same point in the sky gets later each day through the month of December. What is considered high-noon sunlight also becomes later throughout the month.You can check sunrise and sunset times on the National Oceanic and Atmospheric Administration website.