Winter solstice 2016 in Northern Hemisphere was at 5:44 AM on Wednesday, December 21.
The term solstice comes from the Latin word solstitium, meaning ‘the Sun stands still’. This is because on this day, the Sun reaches its southern-most position as seen from the Earth. The Sun seems to stand still at the Tropic of Capricorn and then reverses its direction.
During winter in the Northern Hemisphere, the Earth is actually closest to the Sun. Different seasons are not defined by how far the Earth is from the Sun. Seasons occur because Earth orbits the Sun on a slant, with an axial tilt of around 23.4 degrees. Therefore different amounts of sunlight reaches the Northern and Southern Hemispheres, causing variation in temperatures and weather patterns throughout the year.
For more information check out this informative video on the summer and winter solstice: