WASHINGTON — This season appears to mark the end of Black Friday — at least, as we know it.

For decades, stores have opened their doors in wee hours of the morning on the day after Thanksgiving known as Black Friday. But this year, that changed when major chains from Target to Toys R Us opened on Thanksgiving itself, turning the traditional busiest shopping day of the year into a two-day affair.

That means that shoppers who wanted to fall into a turkey-induced slumber could still head out to stores early on Black Friday.

Others could head straight from the dinner table to stores on Turkey Day.

And stores were able to attract both groups by offering door buster sales from $179 40-inch flat-screen TVs to $10 jeans at different times of the day.

Sam Chandler, 55, and his wife, Lori Chandler, 54, were a part of the early group. By the time they reached the Walmart in Greenville, S.C., early Friday, they had already hit several stores, including Target and Best Buy. In fact, they had been shopping since midnight.

“We’ve learned over the years, you have to stand in line early and pray,” Sam said.

Stu and April Schatz, residents of Rockland County, N.Y., preferred to get a later start. They went to the Shops at the Garden State Plaza mall in Paramus, N.J., which didn’t open until 7 a.m. on Black Friday, because they didn’t want to deal with the crowds that show up for openings late night on Thanksgiving or midnight on Black Friday.

“It’s so much more civilized going in the morning,” said April Schatz, a teacher. “We wanted to enjoy our evening.”

The earlier hours are an effort by stores to make shopping as convenient as possible for Americans, who they fear won’t spend freely during the two-month holiday season in November and December because of economic uncertainty.

Many shoppers are worried about high unemployment and whether or not Congress will be able to reach a budget deal by January before a package of spending cuts and tax increases known as the “fiscal cliff” takes effect.

At the same time, Americans have grown more comfortable shopping on websites that offer cheap prices and the convenience of being able to buy something from smartphones, laptops and tablet computers from just about anywhere. That puts added pressure on brick-and-mortar stores, which can make up to 40 percent of their annual revenue during the holiday shopping season, to give consumers a compelling reason to leave their homes.

That’s becoming more difficult: the National Retail Federation, an industry trade group, estimates that overall sales in November and December will rise 4.1 percent this year to $586.1 billion, below last year’s 5.6 percent growth. But the online part of that is expected to rise 15 percent to $68.4 billion, according to Forrester Research.

As a result, brick-and-mortar retailers have been trying everything they can to lure consumers into stores. Some stores tested the earlier hours last year, but this year more retailers opened their doors late on Thanksgiving or at midnight on Black Friday. In addition to expanding their hours, many also are offering free layaways and shipping, matching the cheaper prices of online rivals and updating their mobile shopping apps with more information.

“Every retailer wants to beat everyone else,” said C. Britt Beemer, chairman of America’s Research Group, a research firm based in Charleston, S.C. “Shoppers love it.”

Indeed, some holiday shoppers seemed to find stores’ earlier hours appealing. Julie Hansen, a spokeswoman at Mall of America in Minneapolis, said 30,000 people showed up for the mall’s midnight opening, compared with 20,000 last year. She noted that shoppers are coming in waves, and sales aren’t just being shifted around.

“This is additional dollars,” Hansen said.

About 11,000 shoppers were in lines wrapped around Macy’s flagship store in New York City’s Herald Square when it opened at midnight on Black Friday. That’s up from an estimated 9,000 to 10,000 shoppers who showed up the store’s midnight opening last year.

Joan Riedewald, a private aide for the elderly, and her four children ages six to 18, were among them. By that time, she already had spent about $100 at Toys “R” Us, which opened at 8 p.m., and planned to spend another $500 at Macy’s before heading to Old Navy.

“I only shop for sales,” she said.

But some shoppers decided to stick to traditional Black Friday shopping hours. Joe Russell was hunting for a great deal on a large flat-screen TV and went to the Best Buy store in Watertown, Mass., shortly after midnight on Friday. But the long line of shoppers gunning for door-buster promotions deterred him from braving the freezing temperatures. So Russell, 47, returned to the store after sunrise and got a different TV for “a decent price.”