The winter solstice marks the exact moment when half of Earth is tilted the farthest away from the sun. It usually happens on December 21 or 22, at the exact same second around the world.

Because less sunlight reaches Earth, the winter solstice is also the day of the year with the least amount of daytime, known as the shortest day of the year. But the good news is that every day after the winter solstice will be a little longer, until we reach the day with the most hours of daylight. Called the summer solstice, it usually occurs between June 20 and June 22.