The Winter Solstice, the moment when the Earth’s axial tilt is fully 23º26′ from the Sun, is tomorrow, Sunday, December 21st, at 4:03 PM MST in the northern hemisphere. It is, of course, the Summer Solstice in the Southern Hemisphere.
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 Sunday is the shortest time between the two, the least daylight of the year in the northern hemisphere.
For more than 1600 years in western Europe the northern winter solstice was celebrated on December 25th, though astronomically it increasingly came later than that due to errors in the Julian calendar.