The Winter Solstice, the moment when the Earth’s axial tilt is fully 23.5º away from the Sun, is tomorrow, Monday, December 21st, at 9:49 PM MST in the northern hemisphere.
It is, of course, the Summer Solstice in the Southern Hemisphere, tilted toward the sun.
The Earth’s orbit is elliptical not circular. The earliest sunset (in the northern hemisphere) was around two weeks ago. The latest sunrise is in about two weeks.
But Monday is the shortest time between the two, the least daylight of the year in the northern hemisphere.
Solstice comes from the Latin solstitium, meaning “Sun stands still.” The Sun has been setting farther south each day (to our perspective). Tomorrow it stops — stands still — and begins moving north again until the June Solstice.