The winter solstice is the day of the year with the fewest hours of daylight.

In the northern hemisphere this date falls in December every year. The winter solstice in 2025 occurs on Sunday, December 21, marking the first day of winter in the Northern Hemisphere. The exact moment of the solstice is at 10:03 a.m. Eastern Standard Time (EST).

This event signifies the shortest day and longest night of the year, with daylight hours varying by location—approximately 9 hours and two minutes in Detroit and 7 hours, 49 minutes, and 42 seconds in London. In Anchorage, Alaska, daylight is only 5 hours and 34 minutes! After the solstice, the days gradually begin to lengthen again until the summer solstice in 2026.

The apparent position of the Sun in the sky changes throughout the year. During the summer months it rises higher in the sky and is above the horizon for longer. In the winter the Sun’s position is lower and its time in the sky is shorter.

This variation happens because the Earth orbits at an angle: it is tilted 23.4 degrees on its axis.

During summer in the northern hemisphere the North Pole is tilted towards the Sun, and therefore this part of the Earth receives more direct sunlight and longer daylight hours. During winter in the northern hemisphere the North Pole is tilted away from the Sun, resulting in fewer daylight hours.

The winter solstice occurs at the point when this tilt away is at its maximum and the Sun is lowest in the sky. This is what gives us the shortest day and the longest night of the year.

If you’re in the southern hemisphere the opposite is true: in December the South Pole is tilted towards the Sun, making it summertime ‘Down Under’.

The further north that you live, the shorter the day will be.

After the shortest day, the days start getting longer and the nights shorter. At the spring and autumnal equinoxes the day and night hours are around the same length, each lasting around 12 hours. The number of daylight hours peaks at summer solstice.

The world ‘solstice’ comes from the Latin ‘solstitium’, meaning ‘Sun stands still’ – because the apparent movement of the Sun’s path north or south stops before changing direction.