In pictures: How revelers marked winter solstice 2021

Every year, on December 21, Earth experiences winter solstice, a phenomenon wherein one of its pole tilts is farthest from the sun, causing the day to become the shortest of the year and the night to become the longest.

A person captures the Manhattan skyline on the Winter Solstice in Brooklyn, New York City, U.S. (Source: Andrew Kelly/REUTERS)

Cedric Vareil of France stands in front of the Manhattan skyline with his daughter on the Winter Solstice in Brooklyn, New York City, U.S. (Source: Andrew Kelly/REUTERS)

Reveller enjoys sunrise during winter solstice at the 5000-year-old stone age passage tomb of Newgrange in the Boyne Valley, Newgrange, Ireland. (Source: Clodagh Kilcoyne/REUTERS)

Dog sits on its owner's face as revellers welcome winter solstice at the 5000-year-old stone age passage tomb of Newgrange in the Boyne Valley, Newgrange, Ireland. (Source: Clodagh Kilcoyne/REUTERS)

Interestingly, this happens twice every year, once in the northern hemisphere and once in the southern hemisphere.(Source: Clodagh Kilcoyne/REUTERS)

the opposite of this occurrence is the summer solstice when one of the poles tilts is towards the sun, causing the longest daylight and shortest night. (Source: Clodagh Kilcoyne/REUTERS)

The tilting towards and away from the sun is the reason why countries situated around the poles — north and south — experience opposite weather conditions in different times of the year. (Source: Clodagh Kilcoyne/REUTERS)

Worker at a restaurant famous for dumplings during winter solstice day in Beijing, China. (Source: Ng Han Guan/AP Photo)

Customer leaves from a restaurant popular for its dumplings during winter solstice day in Beijing, China. (Source: Ng Han Guan/AP Photo)

People hold candles and gather around fire during a winter solstice celebration in North Andover, Massachusetts, U.S.(Source: Reba Saldanha/REUTERS)