Hundreds of Texans are expected to come to downtown Dallas Thursday for an eight-hour string of faith-based celebrations that will include Sikh drummers, Islamic prayers, Hindu singers, a Jewish cantor and Methodist and Baptist congregations.

It may sound like a standard interfaith event, another of the many that have become popular in increasingly diverse American cities, but the revelry at the the city's Thanks-Giving Square in observance of the National Day of Prayer is unique in how far it's departed from its Protestant roots.

The National Day of Prayer, which has been observed on the first Thursday in May for 24 years, is still a largely Christian event, in which millions of Americans from thousands of churches across the country will participate, bowing their heads to God in prayer on the day that traces its history to the nation's earliest years. There will be Bible read-a-thons in front of city halls, police officers will pay tribute to the nation's first-responders at churches, and the devout will descend upon courthouse steps across American cities to grace the buildings with prayer.

But the event, designated via presidential proclamation, has increasingly faced accusations of encouraging an uncomfortable mingling of church and state and being too narrowly focused in practice on Christianity.

On one side, secular humanists and atheists have responded by promoting their own event, Thursday's National Day of Reason. Now in its ninth year, the nonreligious celebration has expanded to more than a dozen cities, where it's observed with blood drives, training on pro-secular policy lobbying and voter registration drives, as well as social events.

On the other hand, believers such as those in Dallas have tried to change the day's legacy by broadening its appeal. The Thanks-Giving Foundation, which typically observes the National Day of Prayer with an interfaith breakfast or luncheon, has made this year's event into a day-long festival, where more than half the events are purposefully devoted to non-Christians.

"We believe in the idea that gratitude is something that all faith traditions and all cultures value," said Chris Slaughter, a Christian Scientist who is president of the Thanks-Giving Foundation, which will be celebrating its 30th National Day of Prayer. "It can be used as a beginning point of conversation to learn about each other to gain respect and understanding."