The winter solstice marks the start of the winter season. It has the shortest day and the longest night. Many countries and religions hold festivals and ceremonies marking the winter solstice, the day of the "sun’s rebirth." It is observed annually in December, and the date may change from year to year.

Resources:

• Britannica - Winter solstice
• Reader's Digest - 13 Fascinating Winter Solstice Traditions around the World
• Time and Date - December Solstice: Longest and Shortest Day of the Year