WARSAW, Poland (AP) — It's that time of year — tradition goes — when the veil between the world of the living and the world of the dead is lifted.

This traditional belief has morphed over the centuries into a spooky and secular celebration Halloween.

But a day later, Christians Many countries around the world celebrate All Saints' Day on Friday, a somber and spiritual day in the church's liturgical calendar that shares pagan roots with Halloween.

The word “Halloween” is derived from “All Hallows Eve,” meaning the eve of All Saints’ Day, a holiday also known as All Saints’ Day. It honors martyrs and saints – those who have been sanctified or are considered holy – a tradition begun by the Roman Catholic Church in the early Middle Ages.

Scientists believe that the spectral aspects of Halloween originated primarily from Samhainan ancient Celtic festival that took place during harvest season, said Morgan Shipley, a professor of religious studies at Michigan State University in East Lansing.

It was a time when people “went from the harvest and the bounty and the bounty of summer to the desolation of winter,” he said. “And it has been said that at this time the veil between the physical, material world of man and the spiritual world essentially dissolves.”

Some of the spirits or spectral beings were considered demonic in nature, and bonfires became a way to ward them off or were used by Druid priests and priestesses for divination as the veil between the material and spiritual worlds broke, he said.

As Christianity spread, many pagan rituals were adapted to the new faith to be more attractive to converts. The time to reflect on the dead lasts until November 2nd, All Souls' Day.

In Central Europe, the Slavic and Baltic peoples had their own rituals in which the living communicated with the dead between October 31st and November 1st.

In many traditional Roman Catholic societies, believers and non-believers alike celebrate this day.

Finka Heynemann, 34, visited Warsaw's Brodno Cemetery with her mother on Friday morning. The two planned to visit six cemeteries in Warsaw within three days – even though they are not religious.

“It’s just important to keep the tradition and visit the graves and respect and honor the ancestors,” Heynemann said.

“This day is more important than Christmas or Easter,” added her mother Maja Gąssowska, pausing to drop money into a collection box for a Polish cemetery in the Ukrainian city of Lviv, once part of Poland.

In PolandMany travel back to their families to meet with those still living and to reflect on those who have left them.

So many people celebrate the holiday that cemeteries are transformed into flickering carpets of light so impressive that even the most worldly people feel moved. Cities like Warsaw and Krakow have many additional tram and bus lines to transport the large number of people to and between cemeteries.

While the thoughts are mostly personal, people also leave candles at the graves of national heroes. So many people visit cemeteries at the same time that the celebration takes on a communal character.

It has become so much a part of the culture in Poland that people also lay candles in Jewish and Muslim cemeteries.

In the PhilippinesMillions flocked to cemeteries across the country on Friday to witness the annual tradition and visit the graves of their loved ones.

“Even when I am old, I still visit my relatives' graves, especially my husband's, on All Saints Day,” said Manila resident Dory Oliquino, who was among thousands who donated flowers and candles at the Manila North Cemetery in the country's capital . “As long as I can walk, I’ll visit him.”

For many Filipinos, All Saints Day is a family gathering where they keep vigil at graves.

“All Saints Day is the day when we celebrate and remember our departed loved ones so that our memories of them remain fresh in our minds even when they are no longer there,” said Luis Montibon.

Italian Traditionally, people visit cemeteries to pay respects to family members who have died on All Souls' Day by lighting candles or laying flowers. Pope Francis will visit Rome's third largest cemetery, Laurentino Cemetery, to celebrate Mass and pray for the dead. The pope visited the same cemetery in 2018 and prayed in an area dedicated to fetuses.

In recent years, as the holiday approaches, there has been debate about Halloween and its compatibility with the Christian belief in the afterlife.

After the fall of communism in 1989, Poles began celebrating Halloween, but some fear that foreign cultural importation may eventually dilute the All Saints' Day tradition. Some Catholics worry that it could also be sinful because of the allusions to devils and spirits. In response, some church groups have begun holding alternative All Saints Day events.

This week, a church group organized the 3rd All Saints Ball in the Polish city of Plock, according to Catholic news site Niedziela – meaning Sunday – which reported that “the children were dressed as saints and blessed by the Catholic Church and such angels.” “

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Associated Press writers Colleen Barry in Milan and Basilio Sepe in Manila, Philippines contributed to this report.