Most of the year, Canadians living in the United States look, talk and act so much like their neighbors that their nationality draws no attention at all. Autumn is a season of danger, though, when the mask of assimilation can be ripped off, forcing some Americans to face the unnerving, if fleeting, realization that Canada is an entirely different country.

All it takes is one mention of Canadian Thanksgiving.

The first reaction is typically laughter, as if this were another fine example of the Canadian sense of humor. Then comes disbelief. Finally, when it emerges that the holiday is celebrated on the second Monday in October, there may be a suspicion that on the other side of the border, time does not behave in the same way.

“It tends to domino into other big holidays,” said Kathryn Borel, a television writer in Los Angeles who grew up in Toronto and Quebec City. “They’ll really carefully ask you: ‘Do you celebrate Christmas on the same day? Do you celebrate — Easter?’ You can see it messing with their paradigm, like, if Thanksgiving is different, what else is different?”

A state of total innocence about Canadian Thanksgiving is easy to maintain in the United States, where the holiday gets about as much attention as the half-birthday of the youngest child in a family of 12. For one thing, it happens on Columbus Day, so eyebrows are not necessarily raised if somebody slips back to Saskatoon to spend the weekend with the family.

For another, the vast Thanksgiving-industrial complex keeps a conspiracy of silence about the existence of a parallel harvest dinner outside the United States. Taste of Home, the American food magazine with the largest circulation, says it has never run any articles about the Canadian holiday, although it has published Thanksgiving recipes from Canadian readers.

“Damn, I didn’t know this was a thing,” said Hunter Lewis, the editor-in-chief of Cooking Light, the food magazine with the second-largest circulation. After some research, Lewis wrote back to confirm that his magazine has never covered the holiday, either. Nor has Bon Appetit, according to a spokesman.

Turkey fatigue, a notorious affliction among food editors, may be partly to blame.

“It’s bad enough having to do Thanksgiving over and over every year,” Ruth Reichl, who edited Gourmet from 1999 until its demise in 2009, wrote in an email. “We never touched a second Thanksgiving!”

If these magazines had asked their stringers to hunt down Thanksgiving dishes in Calgary and Toronto, they would have found the recipes uncannily familiar. The centerpiece of Thanksgiving dinner in Canada is, frequently, roast turkey with stuffing and gravy. Side dishes are made with fall vegetables like sweet potatoes and squash. Dessert will be pie. Everybody’s favorite is pumpkin.

Even Canadians struggle to explain what distinguishes their Thanksgiving table from the American one.

“We eat remarkably the same things,” said the chef Hugh Acheson, who spent most of his childhood in Ottawa and now runs several restaurants in Georgia. “Canada is such a big country, and is still finding its way culinarily, that it’s very much Americanized in terms of what we eat.”

As in the United States, some people augment the turkey with food from the places where they or their grandparents lived before landing in North America. For Hrag Vartanian, who was born in the Armenian community of Aleppo, Syria, and grew up in Toronto, this meant tabbouleh or hummus alongside the turkey and brussels sprouts.

Vartanian, now the editor-in-chief of the art site Hyperallergic, calls himself “a huge fan” of the holiday and tries to observe it with dinner every year in New York City, where he lives. Among other things, he sees it as a better way to spend the day than commemorating Columbus’ kickoff to the European conquest of the Western Hemisphere.

But even after 16 years in the United States, Vartanian isn’t quite sure what sets his menus apart from the ones his U.S.-born friends serve in November.

“It gets to a conversation of what exactly is Canadian food,” Vartanian said. “It’s sort of like an accented cuisine. You’re just trying to find a little thing to put in, maybe some maple candy, to bring in some of that Canadian flavor. You really have to dig.”

Michael Goldbach, a screenwriter in Los Angeles who describes his family as “deeply, boringly Canadian,” said that at their home in rural Ontario, the holiday table was a carnival of blandness.

“I literally remember being excited for the dinner rolls,” he said.

Pressed on whether the Goldbachs had eaten anything out of the ordinary, he finally said, “We did try different kinds of corn.”

Different kinds of corn?

“Where I grew up was corn country, so sometimes there would be an exciting kind of corn,” he elaborated. “By the way, it usually wouldn’t be very good.”

Strictly from a branding point of view, Canada could have done more to position its holiday apart in the public mind. A single distinctively Canadian dish would help. So would a vivid back story. The traditional account of the pilgrims and natives at Plymouth in 1621 may be highly revisionist, but at least it offers something to debunk.

Janie Haddad Tompkins, an American actor who for the past six Octobers has attended Thanksgiving dinners hosted by Canadian expatriates in Los Angeles, said that her hosts never seemed to get around to explaining why their country observes the holiday in the first place.

“I thought our Thanksgiving had to do with the pilgrims and the Indians and all that stuff, which is a real whitewashing of a genocidal moment in our history,” Haddad Tompkins said. “But I don’t know what theirs is related to at all. Except maybe we had one, and they wanted to get in on the fun.”

The Protestant church leaders in Ontario who successfully lobbied for the first national day of giving thanks in 1859 did have their eye on the U.S. holiday, but fun was not high on their list of priorities. According to Peter A. Stevens, who teaches history and Canadian studies at York University in Toronto, these clergymen established Thanksgiving as a religious holiday with an undercurrent of nationalist pride.

“You were supposed to go to church and reflect on the blessings you and the country had received,” Stevens said. Dinner was something of an afterthought until the 1870s and ’80s, when Canadian newspapers began looking to the United States for menu ideas.

(In Quebec, where Protestants are a minority, the new holiday caught on slowly. L’Action de Grace, as it is called, is still somewhat optional, and the turkey-and-stuffing program is far from universal.)

Perhaps because they borrowed the holiday, Canadians who try to explain what makes theirs different tend to focus on the elements that they didn’t take.

Airports do not become thronged sites of panic and despair, they will tell you. Distressingly slow corporate-sponsored balloons do not lumber down the boulevards. There are football games, but nobody really pays attention to them.

When Canadians talk about their Thanksgiving, the word “quieter” comes up a lot. You can start to think that they see their Thanksgiving something like Christmas morning among the Whos down in Whoville, calmly sharing the true spirit of the day without all the hoopla.

“It’s a classic example of the narcissism of small differences,” Borel said. “We are like these uppity little Hobbits taking pride in being a little better, a little more moral, a little more socially conscious than Americans. But when you look at both of us, you can’t see the difference, really. Even on the holiday that you associate with tryptophan comas and drawing hand turkeys, we still need to assert our subtle moral superiority over Americans.”

Perhaps because Canadians don’t expect foreigners to know very much about their country, Americans who are invited to an October Thanksgiving can make a big impression simply by demonstrating a slight familiarity with Canadian customs.

Rick Slater, who was raised in the United States by Canadian parents, hosts a Canadian Thanksgiving each year in his restored carriage house in Brooklyn, where one American guest made a big impression.

“One year somebody came with a lot of doughnuts, because they knew enough about Canada to be aware of their huge, overwhelming importance,” he said. “It was a great dessert, I’m not going to lie.”