Wednesday is Epiphany, a major holiday in much of Orthodox Christianity celebrating the birth and baptism of Jesus. Religious services are held as well as Blessing of Water ceremonies at lakes, rivers and seafronts.
But in Russia, Serbia, Ukraine and other Orthodox countries that observe a different religious calendar, it is Christmas Eve. Roman Catholics and Protestants, meanwhile, celebrate the story of the Wise Men who followed a star to Jesus' cradle.
Here's a look at celebrations taking place on Wednesday:
Ceremonies were held across the country, with divers jumping from piers, bridges and tug boats and including school children and members of the country's navy special forces.
The main ceremony was held at the country's largest port of Piraeus, near Athens, but left-wing Prime Minister Alexis Tsipras attended a smaller ceremony in the Greek capital following a spat with traditionalists in the Orthodox Church who vehemently opposed a recent law sanctioning same sex-civil partnerships.
Bishop Serapheim of Piraeus described the law an "insult to human identity" and "psychiatric deviation from healthy sexuality."
More than 1,000 Orthodox Christian faithful attended the annual Epiphany Day blessing of the waters in Famagusta in Cyprus' breakaway Turkish Cypriot north. It was the first time the ceremony has taken place since 1974 when Turkey invaded after a coup aiming at union with Greece divided the island.
In keeping with tradition, Archimandrite Avgoustinos Karras hurled a silver cross into the cold waters of the eastern Mediterranean as about 20 daring swimmers dashed into the sea to retrieve it. The ritual is called the Blessing of the Water and symbolizes Jesus' baptism in River Jordan.
Organizer Pavlos Lacovou told The Associated Press that several Turkish Cypriots also attended Wednesday's ceremony.
Acting as the backdrop to the ceremony was the Turkish military-controlled suburb of Varosha that has remained a virtual ghost town for 42 years, ensconced in a chain-link fence that keeps everyone out.
The ceremony was the latest in a number of recent, faith-oriented acts of rapprochement between the island's majority Orthodox Christian, Greek-speaking and the Muslim, Turkish speaking populations. They aim to underscore that religion doesn't drive a wedge between Greek and Turkish Cypriots.
Pope Francis says restless hearts these days are seeking sure answers to life's questions but don't find them.
Francis has voiced this reflection during Mass in St. Peter's Basilica Wednesday to mark Epiphany, which recalls the Gospel account of the Three Kings, or Magi, who followed a star to find baby Jesus in Bethlehem.
The pontiff said: "Like the Magi, countless people in our day have a 'restless heart' which continues to search without finding sure answers."
Members of Istanbul's tiny Greek Orthodox community, visitors from neighboring Greece and other faithful attended an Epiphany service led by Ecumenical Patriarch Bartholomew I, the spiritual leader of the world's Orthodox Christians in Istanbul, where the Patriarchate is based.
A group of faithful leaped into the frigid waters of the Golden Horn inlet to retrieve a wooden cross thrown by Bartholomew. Nicolaos Silos, a 28-year-old visitor from Greece, was the first to reach it.
A ceremony to bless the waters was also held in Izmir, Turkey's third-largest city. It was the first "official" Epiphany ceremony there since the end of a Greek-Turkey war nearly a century ago that triggered a population exchange between Greece and Turkey. Although the Greek Consulate in Izmir had organized a ceremony 2006, it was the first time the Turkish government both approved and helped to organize it.
"It's a historic day here and we're grateful to the local authorities and to the Patriarchate ... for making this happen," Tina Samoglu, secretary of the Izmir Orthodox Community told Greek state TV. "I feel very proud and I'm filled with emotion."
The patriarchate in Istanbul dates from the 1,100-year-old Orthodox Greek Byzantine Empire, which collapsed when the Muslim Ottoman Turks conquered Constantinople, today's Istanbul, in 1453.
This will be the first time since 1928 that a Christmas Eve Mass has been held in the world's largest Orthodox basilica, the St. Isaac's Cathedral in St. Petersburg.
The landmark 19th Century cathedral was turned into a museum under the officially atheist Soviet regime; after the USSR's collapse in 1991 it remained as a museum, but the Russian Orthodox church has used it periodically for services.
Thousands of young men waded into icy waters in Bulgaria to retrieve crucifixes cast on the waters by priests. By tradition, the person who retrieves it will be healthy and freed from evil spirits all year. After the cross is fished out, the priest takes a bunch of dried basil to sprinkle water over believers.
In some villages, men dipped into a local river and danced the horo, a traditional dance. In the mountain village of Kalofer, in central Bulgaria, scores of men in traditional dress waded into the icy Tundzha River carrying national flags.
Led by a drummer and several men playing the bagpipes, they danced in the freezing waters, pushing away floating chunks of ice. Some sipped plum brandy and red wine as an antidote to the freezing weather.
Children across Spain woke up Wednesday to open presents left during a night-time "visit" by the Three Kings of Orient, a tradition similar to that of Santa Claus but celebrated annually on Epiphany.
Expectations were raised the previous evening as towns and cities across the country held Epiphany parades or cavalcades symbolizing the coming of the Magi to Bethlehem laden with gifts for the baby Jesus.
Thousands of children and parents thronged sidewalks in Madrid and other cities to watch as ornately decorated floats — including in some cases men dressed as kings riding camels or horses — were accompanied by clowns, jugglers and marching bands.
The tradition spread from Spain to many Latin American countries where Epiphany is the day when gifts are exchanged.
The Orthodox Patriarch of the Holy Land, Theophilos III, arrived in Bethlehem on Wednesday for Orthodox Christmas celebrations. He walked along the streets of the city in the traditional procession toward the Church of the Nativity, which is revered as marking the site of Jesus' birthplace.
Rebels in the east said they were willing to release captives taken during the conflict to mark Christmas. It was unclear however, if Ukrainian authorities would be willing to do a prisoner exchange.
The rebels in Donetsk said they wouldn't engage in a release without a similar release by Kiev. But Igor Plotnitsky, leader of rebels in Luhansk, said his forces were prepared for a release without any reciprocal move by Kiev.
It was not known how many prisoners each sides are holding or how many might be eligible for the potential release.
Hundreds of Romanian villagers gathered on the fields near the southern village of Pietrosani, where a priest blessed horses in a traditional Epiphany ritual to ward off diseases and bad luck during the year.
Orthodox priests sprinkled holy water on more than a dozen horses, which were decorated with red tassels, ear caps and ankle bands for good luck. The animals are essential to village life, and are used for plowing, carrying wood and transport.
Horses, ridden bareback, later thundered across the icy fields in the annual race. Villagers drank plum brandy and mulled wine and ate grilled spicy sausages to celebrate the feast while horses dragged logs to demonstrate their strength.
Several thousand people gathered in Mexico City's huge Zocalo plaza on Tuesday evening to partake in a gigantic Three Kings Day cake known as a "rosca."
The pastry weighed 9.3 metric tons and formed a loop that was 1,440 meters long.
Mexico City's local government sponsored the free event, which is held annually, and Mayor Miguel Angel Mancera was on hand to cut the cake.
The Three Kings are beloved in Mexico, as in other parts of Latin America, by children who wait for the wise men to bring them gifts on Epiphany eve.
In New Orleans, Carnival season begins on Jan. 6 — the "Twelfth Night" after Christmas. The Carnival season is celebrated along the Gulf Coast with parties, balls and parades culminating on Mardi Gras, or Fat Tuesday, a final day of celebration before the solemnity of Ash Wednesday and Lent. Mardi Gras falls on Feb. 9 this year. The countdown to Mardi Gras is marked by a streetcar full of raucous costumed revelers. The group known as the Phunny Phorty Phellows kicks off Carnival season Wednesday night by riding a streetcar through the city along famed St. Charles Avenue. And bakeries across the city have started churning out king cakes — an oval-shaped pastry with a plastic doll hidden inside. Whoever finds the doll is dubbed "king" and buys the next cake.
In the U.S. territory of Puerto Rico, a worsening economic crisis has for the first time dampened a popular government-sponsored celebration of Three Kings Day that typically draws thousands of families.
The Puerto Rican government, which was criticized in 2011 for giving out laptops to children amid an economic crisis, announced this week that it would greatly scale back this year's celebration and would only hand out a limited number of balls to children.
Officials also moved the territory's annual celebration to the central mountain town of Utuado, which agreed to pick up part of the bill because of the central government's dwindling cash flow.
In previous years, families formed long lines overnight in the capital of San Juan to receive gifts from the government.
Epiphany is linked to a major charity event, which some 60,000 to 70,000 volunteers all across the country take to the streets to collect money to help people in need at home and abroad.
Last year, they collected about 90 million koruna ($3.6 million). The collection is organized by the Caritas Czech Republic, a charity organization of the Roman Catholic Church. Ten percent is designed for aid abroad.
In Prague, the capital of the Czech Republic, dozens of polar swimmers braved heavy snowing and freezing temperatures to take part Wednesday in the traditional Epiphany swim in the Vltava River near the famed Charles Bridge.
President Andrzej Duda, the first lady and hundreds of residents walked in a cheerful Epiphany procession in sub-freezing temperatures in downtown Warsaw.
The procession was led by Cardinal Kazimierz Nycz, the archbishop of Warsaw, and by colorfully dressed actors in the roles of the Three Magi, riding on a camel, a horse and a paper dragon. It ended with the crowd singing carols in the central Pilsudski Square.
Similar processions were held in other cities across the predominantly Catholic Poland, which will be marking 1050 years of Christianity in April.
Egyptian Copts are expected to flock to Cairo's Orthodox Cathedral to attend Christmas services on Wednesday amid tightened security ahead of the 2011 uprising's anniversary. Fears of potential attempts to mark the anniversary of the revolt with protests have been on the rise in recent weeks.
Egypt's Orthodox Coptic Christians make up about 10 percent of the country's 90 million people. The Copts have long complained of discrimination in Egypt and largely supported the military's overthrow of the first freely elected President Mohamed Morsi in 2013 after one year on office. Ever since, Christian gatherings are believed to be at an even greater risk of militant attacks.