WASHINGTON — Thanksgiving is an official American holiday that celebrates one of the country’s founding myths.

It is famous for a huge meal and family fights around the dinner table, in recent years often over President Donald Trump.

It also marks the start of the Christmas shopping season.

What day is it?

Thanksgiving doesn’t fall on a specific calendar day but rather on the fourth Thursday of November each year.

Who started it?

Abraham Lincoln declared Thanksgiving a national holiday in 1863, although harvest festivals were already traditional.

Wasn’t it the Pilgrims?

Thanksgiving is inspired by a 1621 feast held by the group of Protestant Puritans known today as the Pilgrims after their first successful harvest in the “New World”.

After landing on the Mayflower in what is today Massachusetts the previous year, half died over the hard winter. The newcomers had to rely on help from Native American tribes or in some cases stole from them.

But weren’t they friends?

Wampanoag Native Americans, some of whom were at the first Thanksgiving, helped the settlers learn to farm. They signed a treaty in the spring before the mythic feast, but settlers later tried to take their lands. Many Native Americans do not celebrate Thanksgiving.

So what happens?

Americans have the day off and generally gather for a feast and watch an American football game on television. Also on TV is the Macy’s Thanksgiving Day Parade. Three hours long, it is said to be the world’s biggest and is known for its huge balloons that are trailed between the skyscrapers of New York’s Fifth Avenue.

Sounds like fun

Not always. Family tensions over politics may boil today over Donald Trump but they are nothing new as Woody Allen’s 1986 film “Hannah and her Sisters” showed.

And nothing caught the mad dash to get home on time better than Steve Martin and John Candy in “Trains, Planes and Automobiles” (1987).

What’s on the menu?

Back in the 17th century the first Thanksgiving was heavy on deer, corn and shellfish. Nowadays a common menu consists of turkey with stuffing, mashed potatoes, cranberry sauce, green bean casserole, and an array of pies, usually including apple and pumpkin.

Where else is it celebrated?

Canada, Brazil, Liberia and the Caribbean islands of Grenada and Saint Lucia have their own versions of the feast (dates vary).

Black Friday

The day after Thanksgiving is called “Black Friday” and is the biggest shopping day of the year in the US, with eye-catching discounts. It is considered the start of the Christmas shopping season. It is so called because it often pulls retail businesses out of the red into the black.