It's not just Santa who comes once a year - many non-religious people are drawn back to the church at this time, writes Fionola Meredith.
Wrapped up warmly against the winter night, throngs of midnight worshippers join together to celebrate the birth of Christ with bread and wine. Wide-eyed children, allowed to stay up late for once, gaze around in wonder at the dimly-lit church, made strange and lovely by hundreds of glimmering candles and the spicy scent of fir. It's an enchanting spectacle, and an enriching and deeply affirmative spiritual experience for the thousands of Christians who take part in similar Christmas celebrations across Ireland. But many faces in the Christmas Eve congregation are unfamiliar to regular worshippers.
The same scenario unfolds in churches on Christmas Day, when the ranks of the faithful are swelled by strangers: once-a-year attendees who won't be seen again until another 12 months have passed.
What draws these outsiders to church at Christmas? Barbara (38) describes herself as a non-Christian, who lost her faith as a young woman. Brought up in England in the high Anglican tradition, she has lived in Ireland for more than 10 years. But most of her friends don't know that she attends the midnight service at her local parish church every Christmas Eve, slipping in late and sitting at the back. Why doesn't she tell them?
"Everyone who knows me would be shocked if they saw me in church, because I've made it very clear that I've no time for God in my life. For instance, I recently had a non-religious naming ceremony - with 'godless' parents instead of godparents - as an alternative to christening my youngest child. But I associate the ritual of attending church on Christmas Eve with my own childhood. I left home at a very young age, and lost touch with most of my family. When I attend the Christmas midnight service, it reminds me of those childhood feelings of warmth, security and excitement when I was squeezed into a pew with all my sisters. I suppose my 'secret' church-going is a kind of remembrance of times past."
How do clergymen and women interpret the motives of strangers - both believers and non-believers - who descend on places of worship at Christmas? The Rev Ben Neill, Church of Ireland Rector of St Patrick's in Dalkey, Co Dublin, admits that nostalgia is a big part of the draw: "There's a harking-back to the perceived ideal of family life associated with Christmas." Rev Roy Cooper, of the Methodist Church in Ireland, agrees that secular rather than religious sentiments may be propelling people out of their armchairs and into the pews: "Often they're trying to recreate or recapture something of the past, and Christmas carols conjure that up very well. But even among those who may not use Christian vocabulary, there is a longing to believe that what has been proclaimed really is true."
Rev Neill, too, believes that there is "a yearning for meaning that's deeper than nostalgia, a growing feeling that material prosperity isn't everything. "People are asking, 'is that all there is?' We want to help in the pursuit of that deeper reality."
Fr Eddie O'Donnell, parish priest of St Anne's in Dunmurry, near Belfast, attributes similar motives to the strangers who appear among the familiar faces in his own congregation: "It's dark and overcast at this time of year, and people are instinctively attracted to the music, the warmth and the colour of Christmas celebrations - the red, the green and the gold. And I like to think that that many are unconsciously drawn to the great story of the nativity play itself, not just as a circus event, but out of a sense of restlessness, a need for deep, heartfelt peace. I think it's a kind of homesickness for God."
"It's about touching base," agrees Rev John Faris, a Presbyterian minister in Cork. "It's easy for preachers to bang on about how materialistic Christmas is getting, but there are many people out there who want to connect with Christ. The nativity is all about the extraordinary connecting with the ordinary, the eternal becoming earthed, and people respond to that."
Cathal Duffy, pastor of Castlebar Christian Fellowship in Co Mayo, thinks that this often unspoken but deeply felt desire for the spiritual means that Christmas will never become totally secular, concerned only with "glitter and sentimentality". But some non-Christians are offended by the way many clergy assume that the act of attending a church service on Christmas Eve indicates the presence - beneath the brittle atheistic exterior - of a warm Christian heart secretly beating.
Others feel judged, and implicitly excluded. Maureen, a teacher in her 30s, says, "I attend Midnight Mass with my family every year, but it's nothing to do with belief: it's about tradition, and I enjoy the music. I haven't gone to Mass as a believer since I was a teenager. But I haven't felt as welcome in recent years. The priest is likely to say, 'There are lots of faces we haven't seen during the year' or something similar. How would he know the complex spiritual or secular reasons that cause people to attend? We need to open up to other kinds of religious journeys, to move beyond a narrow understanding of faith."
But there are seasonal alternatives open to those who like their Christmas carols neat and free of liturgical interventions.
Anthropologist Tony Buckley is curator of community life at the Ulster Folk and Transport Museum in Cultra, Co Down. He organises the very popular Carols by Candlelight at Kilmore Church in the grounds of the museum. The small Protestant Episcopalian church, originally built in Crossgar in 1790, hosts eight to 10 carol services each year. "It can hold up to 180 people if you shoehorn them in," says Buckley. "It's a crazy situation - we have never advertised these events, but every year we are turning away people in their thousands because we simply can't fit them in."
The carol services are entirely secular - "just an opportunity for people to belt out carols" - and are now in their 19th year. What's the secret of their success? Buckley says: "The church itself is a nightmare: it's lit only by paraffin lamps and candles, which drip hot wax on people, the benches are hard, narrow and uncomfortable, and the coal-burning stove doesn't make much impact on the freezing cold of the building. But it's precisely that rough-and-ready atmosphere that accounts for its appeal. It's an adventure - people feel they are slipping into the past, capturing an authentic sense of what community life was like then."
It seems that Christmas leaves many with a sense of something missing, perhaps experienced as a yearning for the sacred, a mourning for childhood innocence or a longing for a community connection.
But many people are filling this gap with a mythologised sense of past times, where the candlelight and the carols, not the baby in the crib, have become for them the highlight of Christmas.