Winter Solstice

The winter solstice occurs when the northern pole of Eberron reaches its maximum tilt away from the sun. This marks the day with the shortest period of daylight and longest night of the year on the continent of Khorvaire, and when the sun is at its lowest daily maximum elevation in the sky. To the far north, the polar region experiences continuous darkness or twilight around its winter solstice.
The opposite is true to the south on the continent of Xen'Drik.