From the millions spent on candy each year to Halloween’s global influences and celebrations, here are interesting facts about one of our favorite holidays.

1. It All Began in Ireland

The ancient Celtic Festival called Samhain was first celebrated more than 2,000 years ago in County Meath. The Celts believed it was a time of transition, when the veil between this world and the next came down, and the spirits of all who had died that year moved on to the next life. But if the boundaries between the worlds of the living and the dead overlapped, the deceased could come back to life and wreak havoc among the living. Not a good thing.

Today the ancient past and the twenty-first century come together at the annual Spirits of Meath Halloween Festival, where a re-enactment of the Celtic celebration kicks off with a torchlit procession through town. The Irish welcome Halloween with bonfires, party games and traditional food, including a fruitcake that contains coins, buttons, rings and other fortunetelling objects. In ancient times, it was believed that if a young woman found a ring in her slice, she’d be married within the next year.

2. Globetrotting for Halloween

Halloween festivals in New Orleans, Bangkok, Los Angeles, New York and Limoges, France have become must-see stops on the grown up global party scene. Folks looking for a spookier way to celebrate head to historical haunts in Salem, Massachusetts and the Dracula sights in Romania, while daredevlls can get their spook on at one of the 2,500 haunted attractions worldwide, which has become a $300 million industry.

3. Day of the Dead Isn’t Halloween

Despite outward similarities — sweet treats, skeletons, people in costumes, and other graveyard and death imagery — Halloween and the Day of the Dead (Día de los Muertos) are very different holidays. While Halloween promotes fear of the dead, Día de los Muertos celebrates the dead. The Nov. 2 holiday is a day for people in Mexico, parts of Central and South America, and increasingly throughout the United States to honor their ancestors and loved ones who have passed away and invite those spirits back into their homes to be part of the family once more.

It's a tradition that dates back thousands of years, to the Aztec people. But when the Catholic faith became entrenched in South America, the timing of festival of the dead was changed to coincide with All Saints Day and All Souls Day. This connection is part of the reason why people confuse the holidays.

4. The Timing Is Important

The name Halloween is a contraction of All Hallow’s Evening, also known as the night before All Saints Day (“hallow” is the Old English word for saint). Christians around the world have marked the Triduum of All Hallows since the 8th century AD. The three-day observation includes All Hallows' Eve (Hallowe'en), All Saints' Day (All Hallows') and All Soul's Day, and lasts from October 31 to November 2. It is a time to remember the dead, including martyrs and saints.

5. Trick or Treating Was Put On Hold During WWII

Trick or treating has been part of North American Halloween festivities since the early 20th century but like so many aspects of this holiday, it evolved from an ancient European custom. On All Souls Day, poor people would visit the houses of their wealthier neighbors for a "soul cake" — a form of shortbread — in return for which the beggars promised to pray for the dead of the household. Known as “souling,” the practice was later taken up by children, who would go from door to door asking for gifts such as food and money. Irish and Scottish communities in the US revived the tradition, although it was put on hold for several years during WW II due to sugar rationing. But in the U.S., instead of buying shortbread, Americans will purchase almost 600 million pounds – or $2.8 million worth — of Halloween candy for trick or treaters.

6. Philippines: Singing Hymns For Tortured Souls

People in the Pampanga province of the Philippines observe Pangangaluluwà from October 29 till 31, leading up to All Souls’ Day on November 2. Traditionally, Filipino children have gone from house to house singing hymns about the souls in Purgatory and asking for alms to pay for special masses, but today Filipino children have begun to embrace the ‘trick-or-treat’ tradition and add dressing in costume and asking for sweets to the ritual.

7. People Wore Masks so Ghosts Couldn’t Recognize Them

Back in the day, the Celts worried about bumping into the ghosts they believed came back to the earth on Halloween. To avoid being recognized, people would don masks when they left their homes after dark in hopes the ghosts would mistake them for fellow spirits. These days folks are willing to spend a bundle in their attempts to be mistaken for pop culture icons and internet memes: In total, Americans will spend $2.6 billion on costumes with $1 billion on children's costumes, $1.2 billion on adult costumes and $330 million on costumes for pets, according to the National Retail Federation (NRF).

Princess, animal and superhero costumes are the top three choices for kids, while pet owners say the top costumes are pumpkin and hot dog with the devil and cat tied at third. One major new trend in 2013 is an increase in DIY costumes, which the NRF attributes in part to the rise of Pinterest, which 9.3 percent of people surveyed say they plan to scour for inspiration. The average person will spend $27.85 on a costume, whether from the store or homemade, down slightly from the $28.65 spent in 2012.

8. Halloween in Hong Kong

The city’s East meets West history and a rich folklore filled with ghosts and demons make Hong Kong a natural for Halloween celebrations. For the month of October, there are various celebrations around town including the Scream-No-More Challenge at Hong Kong Disneyland (where you get points for not reacting to scary things) and Tim Burton-esque spooky decorations and foods. There are also events at various malls and attractions around town, even a Halloween themed playground.

9. Jack O' Lanterns Scare Off Evil Wandering Spirits

Carved pumpkins are another old school tradition, originating in Ireland, Scotland and England, where people carved menacing faces into vegetables and placed a candle inside to scare away the evil wandering spirits. Using pumpkins is an American spin on the ritual – the first lanterns were made from hollowed out turnips, rutabagas, gourds, potatoes and beets.

10. Halloween Sales Skyrocket in the UK

The popularity of Halloween continues to grow worldwide. Look a the UK market where 10 years ago, consumer spending on Halloween totaled £12m, now it is a £300m+ industry. One popular British grocery chain saw sales of spider cupcakes and chocolate brownies rise 19 percent from 2011-2102, with sales of Halloween-themed chocolates jumping 86 percent in the same time.

While Halloween celebrations are on the rise in Britain and across the Commonwealth, many lament that it’s at the expense of the centuries-old celebration of Guy Fawkes Day, a night of bonfires and fireworks that commemorate a 1605 Catholic plot to blow up England's Parliament and bring down King James I. Those festivities begin with children making an effigy of "Gunpowder Plot" conspirator Guy Fawkes and parading him down streets, asking passers-by to "spare a penny for the Guy." They would then use the money to buy fireworks and burn Guy on a bonfire. But while older Brits dismiss Halloween as an American holiday (one 2006 survey found that over half of British homeowners turn off their lights and pretend not to be home on Halloween), younger generations now enjoys a veritable witches’ cauldron of Halloween fun, bubbling over with hundreds of ghoulish things to do, from tricks and treats to huge all night warehouse raves and Halloween ghost hunts in haunted houses.