On church calendars, parents and grandparents circle this December event with red ink.

The problem for clergy is simple: When do they schedule that special Christmas service, or that concert full of Christmas classics?

"Evangelicals, and especially Baptists, tend to be rather pragmatic about these decisions. We want the most bang for our bucks and we want as many people as possible" in the pews, said Joshua Waggener, professor of church music and worship at Southwestern Baptist Theological Seminary in Fort Worth, Texas.

One thing is certain: "You have to have those little kids up there singing 'Little Drummer Boy.' It's pragmatic. For most people, I don't think theology has anything to do with" the timing.

This reality affects when churches schedule special events, especially in December -- when their members wrestle with school calendars, travel, office parties, family traditions and, yes, worship services. Meanwhile, civic groups, shopping malls and mass media offer "The Holidays," a cultural tsunami that begins weeks before Thanksgiving.

In churches with centuries of liturgical traditions, the Nativity of Our Lord Jesus Christ is Dec. 25, following the quiet season of Advent (Latin for "toward the coming"). This year, Christmas falls on Sunday and, for Catholics, Anglicans and others, the Christmas Eve Midnight Mass is one of the year's most popular rites. This opens a festive season that continues through Jan. 6, the Feast of the Epiphany. Many Eastern Orthodox Christians follow the ancient Julian calendar and celebrate Christmas on Jan. 7, after Nativity Lent.

In the United States, some kind of Christmas Eve service remains the big draw, according to almost half (48%) of Protestant pastors contacted in a new study by Lifeway Research. The frequency of high-attendance church events builds until Christmas Eve, then declines sharply.

In this survey, mainline Protestant clergy (60%) were more likely than evangelicals (44%) to say Christmas Eve rites drew the most people, with Lutherans (84%) being the most likely to worship on Christmas Eve. In general, evangelical pastors (30%) said their high-attendance events came during the third week of December (30%).

Some churches fared better than others with events earlier in December. Lifeway found that Pentecostals (18%) and Baptists (15%) were more likely than Methodist (3%), Restorationist (Church of Christ) Movement (2%) and Lutheran (1%) leaders to say their highest attendance marks were in the second week. Pentecostals (45%) and Restorationist (37%) pastors were, along with Baptists and other evangelicals, most likely to see big crowds in the third week.

Meanwhile, clergy in the South (39%) were least likely to pinpoint Christmas Eve as their main service. Churches with fewer than 50 attending (19%) were the least likely to stress mid-December events.

Waggener said he has watched these patterns evolve throughout his life -- as a child, a parent and while teaching at seminaries. Growing up Southern Baptist in Northwest Louisiana, the Christmas Eve service was the big event, with his mother always singing "Sweet Little Jesus Boy," a classic gospel song.

"We sang 'Silent Night' with our candles lit at the end of the service -- as the last thing before we went home. That meant it was Christmas," he said, reached by telephone. "You cherished that time at Christmas with family. That was part of us all being together. … I continue to seize every chance that I have to worship with my parents on Christmas Eve."

However, church members traveling to be with family elsewhere is, of course, one reason ministers struggle to know when to schedule Christmas cantatas, children's concerts, live Nativity scenes and other festivities and services. Waggener noted: "You have to put things like that before everyone hits the road and lots of your people are too worn out to take part."

At Southwestern seminary, Waggener said he has started to see another trend -- especially among students from home-schooling families and those who attended Christian classical schools, which emphasize classic literature and ancient languages. Even "die-hard Baptists and evangelicals" are expressing interest in traditional services rooted in scripture and prayers, he said.

"Many of our students are yearning for ways to avoid the rush that surrounds Christmas these days," said Waggener. For example, when he discusses rites linked to the Advent season, "students welcome it. They're asking, 'What traditions can we use? What are our options for our families and our churches?' "