Before Christmas became a commercial festival, it had a spiritual purpose. Houses across the country would light candles in every window to welcome strangers in from the cold, a metaphor for the birth of Christ.
This has evolved into flickering fairy lights and festive displays that can be seen from space. While some deride these light spectaculars as garish, those behind them often have the most Christian of motives.
Here we meet five of them.
Michael and Patsy McCarthy, Askeaton, Co Limerick
While Christmas is a time of joy and celebration for most families, for some it is a reminder of those who are no longer with us. Michael and Patsy McCarthy are brothers who go out of their way to mark that fact
"For the Millennium, we planted a seven-foot oak tree in the middle of the green," says Michael. "Today it's four foot wide and 35 feet high. We cover it in lights every year, but we also put little silver balls all over it, each one inscribed with the names of the Irish soldiers who died in the Lebanon.
"A neighbour of ours went over and a lot of his friends were killed. He came to us with the idea. We put their name and rank on the balls and, in the early years, the army brass and the people belonging to the soldiers came along to the lighting-up. But we don't really have a big ceremony any more. We have five blank balls for the ones who were never located, and add a new ball each year to represent all the local people who died as well."
The brothers live in adjoining houses and they were festooning them in lights long before anyone else in the area. "I'd say about 25 years," says Patsy. "We used to get stuff off the cousins in America. But sure, they don't come home as much any more. You can get most of the stuff in Ireland now."
Michael adds: "I wouldn't be exaggerating in saying we would use 10,000 little lights on just one house. There's a projector on the ground lighting up the areas we can't reach with the words 'Merry Christmas', and we pre-buy the power. It costs around €50 to €60 a week for four weeks."
What makes Patsy do it year after year? "The wife," he says, laughing. "Sure, Christmas is just another day to me. I worked every one for 40 years. Christmas Day, St Stephen's Day, New Year's Day -- it didn't worry me at all. But If I suggested not doing this I'd be ate. Neither of us drinks or smokes, and if we did we'd spend the same amount of money on that. And it's great for the kids."
Liam Tilly, Bath Avenue, Dublin
"It's all junk now," says Liam, referring to the Christmas decorations on sale today. "All cloth Santies who don't sing and lights that don't last." That may be the case, but Liam has spared no expense in making sure his garden still shines.
He spent hundreds of euro acquiring the reindeer pulling Santa's sled. "They're decoys used by hunters to lure the real thing into the firing range," he says.
There are singing Rudolphs and a life-size Santa and twinkling LEDs all the way from Canada. "No one can fix them when they break," he admits.
Liam has been doing his house up for the past 17 years, seven of which have been fundraisers for Our Lady's Hospice and Care Service in Harold's Cross, Dublin.
On the Monopoly board of Christmas-lit houses, he has the prime real estate. "I turn the lights on in early November so I can catch the rugby crowd on their way to the Aviva," he says.
Since 2011 he has raised €40,000, though not without incident. "One year, someone made off with the charity box I had in the garden, but they won't make off with it again. The hospice made me a solid steel drum and it took five people to lift it into the garden."
When Liam is late putting his decorations up -- or even on during the day -- adults and children alike knock on his door, eager to see his winter wonderland (five do so in the 15 minutes I spend with him).
"People walking by can throw a few bob into the shoot on the wall or they can come into the garden to have a look.
"I have sweets for the adults and little cuddly toys for the kids, and throughout the season people knock up to me with bags of coins, 10c and 20c pieces they've been putting aside for the year."
Mick and Phil Maher, Sallynoggin, Co Dublin
Asked why she goes all out on Christmas lights, Phil Maher laughs and says: "A lack of childhood. I got an orange for Christmas one year and I thought, 'This can't be right. There has to be more than this'.
"I never wanted that for my kids, and when people started driving into our estate just to look at the lights, Mick threw up an old ballot box and we've raised at least €30,000 for the Children's Hospital Crumlin."
Mick adds: "They've used it towards the cost of new private wards for cardio and cancer patients and for accommodation for parents of sick children. But most of our money goes towards research."
The couple had personal reasons for picking the hospital -- their daughter had major heart surgery there when she was two.
"We start shopping for the next year's display in the January sales," says Phil. "We have three sheds, a full attic and a conservatory you can't get into because they're stuffed with decorations.
"A couple recently visited us from Glasthule to see the lights they had donated. Their father had died the year before and he used to love doing his garden up, so they were delighted to have found such a good home for his stuff."
"The community has been amazing," adds Mick. "I got a cheque off of a guy in Deansgrange TP Tyres for €150 to help with the cost, and on the day of our lighting ceremony Four Star Pizza came down and gave out free grub while a local shop provided tea and sandwiches."
Even Mick's pet rabbit, Snowy, chipped in. "When poor little Snowy passed on, Phil was looking at his hutch and thought, 'I can do something with that'.
"She put Perspex glass on the front, added electrics and the next year that was the manger."
Peggy and Donal O'Callaghan
Codrum, Macroom, Co Cork
In a statement that's sure to get somebody's fairylights in a twist, Peggy O'Callaghan is convinced that her Macroom home was the first in Ireland to be festooned with Christmas decorations.
"We've been doing it since my eldest boy was four," she says. "And he's 38 this February."
People came from miles around, causing traffic jams outside the house.
Their front garden is more than an acre, with two arches 50 feet apart connected by strings of light, each bearing a Happy Christmas sign. There are Santies, snowmen and reindeer suspended in the air, hanging off roofs or waving out of trees.
Peggy says: "There are candles and shooting stars and at night you can't see the ropes holding them there so it just looks like they're floating by themselves."
The driveway is 120 feet long, lined with toy soldiers and lit by candy canes imported from the States that lead all the way up to the house. Inside is fully done up, too.
Peggy adds: "It has an alpine theme, with bears, snow and even a ski slope. Donal covered the conservatory with black felt and attached lights to make it look like twinkling lights in the night sky. I did a village theme. All the mammies and daddies and kiddies have their pictures taken.
"I've had people who had their pictures taken with their parents coming back with their own children."
Preparations begin in August.
"We hired a big cherry-picker to come and put the LED lights on the big sycamore trees (the tallest is 80 feet high)," says Peggy.
"Since switching to LED lights from the traditional coloured lights, our electricity bill has been a lot smaller, but it cost me €5,000 for the decorations on the 100-year-old sycamore alone.
"We do it to raise money for the senior centre in Macroom, who do fabulous work. Since it's too much effort to take the lights down once they're up, they can look lovely when you're having a barbecue during the summer."
However, the O'Callaghans lock the gates now since their inflatable Santies and a charity box were stolen one Christmas Eve.
"You can just buzz on the gate and we'll let you in. It's better than having kids running around and tripping over the wire," says Peggy.
"We start dismantling on January 6 and I feel bare for the first couple of days when they're gone. I'd leave them up every day if I could."
Declan & Joanne Whelan-Scully
"I remember years ago when I was younger and coming home at two or three around Christmas, just to see a light on made you feel like you were not alone," says Declan. "The winter is dark and lonely, but lights on make you feel good.
"You have to celebrate Christmas. I remember mothers who had nothing but with trolleys full to the brim when I was growing up. We give the same answer they gave when people ask about our bills -- worry about January in January.
"People get a lot of pleasure out of it. When I come home and kids are at the gate I'll wait so I don't disturb them.
"But it can be embarrassing when you are wandering about in your shorts and you look up and there's a crowd outside looking in!"
More people in Kilbarrack put lights up than in other areas, but the tradition isn't as strong as people get older and their children don't carry it on. This has benefited the Whelan-Scullys, though.
"Our neighbour gave us a box of his decorations and people always comment on them," says Joanne. "They are the decorations of Christmas past. We have a choirboy and girl and this ugly elf with pointy ears. The new committee, the KFCRA, post pictures on Facebook and encourage people to come round. It brings the community together."
The lights have also taken on a further purpose as the couple's son, Alex, is autistic. "We're trying to get him to become aware of Christmas," says Joanne. "So we keep saying 'Ho, ho, ho' and point at the lights and decorations. He loves them."
There is a school at the top of the street for children with autism. "They are taken down to our garden every year on a walk and they come in and touch Santa. It's a tradition," says Joanne. "We didn't know autism was going to come to our family, so we understand why it is so big a deal for them."
Joanne admits she's a curtain twitcher. "The minute I hear a noise, I'm up out of my seat looking out.
"I would love to raise money for autism, but I get stressed out at the thought of someone robbing me. I'm a native of Ringsend and I really admire the work that Mr Tilly (Liam) does. For someone to come along and steal that money ... it would infuriate me.
"But I'm going to keep putting lights up. Patrick's Day is a day, Halloween a night. Christmas is a season, a season of goodwill."