Everything You Need to Know About the Winter Solstice The winter solstice occurs annually when the sun reaches its most southerly declination, when the North Pole is tilted farthest from the sun. The word solstice means "sun stand" or "sun stands still." For the southern hemisphere, this day marks their summer solstice, which is the longest day of the year. The shortest day of the year lasts for 7 hours, 49 minutes and 41 seconds in Britain. The shortest day of the year often falls on Dec. 21, but due to the 365-day modern calendar, we have an extra day every four years, thus the solstice can happen between Dec. 20-23. The day after the winter solstice marks the beginning of lengthening days, leading up to the summer solstice in June.