On Christmas Day in the United States, Americans wake up around 7:35 a.m. on average. They might be envious of Brazilians, who have languid Christmas mornings and whose average wake-up time is 9:09 a.m. The Japanese, meanwhile, wake at 6:43 a.m., about the same time as every other day.
The difference seems to be whether a country's main holiday celebration is on Christmas Eve or Christmas Day (or not at all) — and that can be traced to religious tradition. The most Roman Catholic countries sleep in latest, probably because many people stay out later on Christmas Eve, often attending midnight Mass.
The latest-rising countries — Brazil, Spain and Belgium, where people sleep past 9 a.m., according to data from 500,000 wearers of the Jawbone UP activity tracker — are also more than three-quarters Catholic. In each, the big meal is on Christmas Eve — it's not typically served until 10 p.m. in Brazil, followed by midnight Mass.
In Spain, after Mass, some people walk through the streets playing music, according to WhyChristmas.com, a website about Christmas traditions. A Spanish Christmas Eve saying translates to: "Tonight is the good night and it is not meant for sleeping."
Some of the countries that rise earliest go about business as usual on Christmas Day, like Japan, where Dec. 25 is not a national holiday. Japan is one of the least religious countries in the world, according to a survey by WIN/Gallup International, and Catholics are extremely rare there.
Most early risers celebrate on Christmas Day. In South Africa, where the average wake-up time is 6:43 a.m., many attend Christmas morning church services, according to WhyChristmas.com. That is followed by a midday meal and outdoor activities in the afternoon, because it is summer there in December. Ninety-one percent of South Africans say they are religious, Gallup found, and 6 percent are Catholic.
Australia, where people tend to awaken just after 7 a.m., also commonly has a traditional midday meal on Christmas Day instead of an evening one the night before.
In the United States on Christmas Eve, people go to bed 44 minutes later than usual on average, at 11:54 p.m., and wake the next morning 50 minutes later, at 7:35 a.m. — many probably pounced on by small children eager to see what Santa Claus left under the tree overnight.
Christmas has become largely cultural for many Americans: 87 percent of people who are not religious say they celebrate it, according to the Pew Research Center, and one-third of Jewish Americans do (often because they have a non-Jewish spouse.) Americans are more likely to say they celebrate with friends and family than at religious services.
Just over 20 percent of Americans are Catholic, but only 16 percent of them say they have high involvement in their church, the lowest share of any Christian denomination except Episcopalians, according to Pew.
Overall, people don't sleep more over the holidays — they just go to bed later, and sleep in.