People line up to get into a store on 5th Ave. looking for Black Friday sales in New York November 29, 2013. Black Friday, the day following Thanksgiving Day holiday, has traditionally been the busiest shopping day in the United States. [Agencies]

More than a dozen major retailers from Target to Toys R Us opened for 24 hours or more on Thanksgiving Day through Black Friday, the traditional start to the holiday shopping period. As a result, crowds formed early and often throughout the two days.

About 15,000 people were waiting for the flagship Macy's in New York City's Herald Square when it opened at 8 pm on Thanksgiving. Long checkout lines formed at the Target in Colma, Calif., on Black Friday morning. And at North Point Mall in Alpharetta, Ga., Jessica Astalos, 20, had already been shopping for six hours starting on Thanksgiving night as another wave of shoppers made their way into the mall around 5:30 am on Black Friday.

"I like being around crowds of people all doing the same thing," said Dalton Mason, 22, of Stockbridge, Ga.

The start of the holiday shopping season has transformed into a two-day event. For nearly a decade, Black Friday had been the official start to the busy buying binge sandwiched between Thanksgiving and Christmas. It was named Black Friday because that was traditionally when retailers turned a profit, or moved out of the red and into the black.

But in the past few years, retailers have pushed opening times into Thanksgiving night. Some like Macy's opened on Thanksgiving for the first time this year. Others like Gap Inc., which owns Banana Republic, Gap and Old Navy, opened some stores earlier on Thanksgiving than the year before. And many pushed up the discounting that used to be reserved for Black Friday into early November.

The earlier openings and sales were met with some resistance. Some workers' rights groups had planned protests on both Thanksgiving and Black Friday because they opposed having retail employees miss family meals at home. But as of Thursday afternoon, there weren't reports of widespread protests.

Some shoppers even had said they would not venture out on Thanksgiving because they believe it's a sacred holiday meant to spend with family and friends. And at least one who did venture out regretted the decision. By 5 am Friday, Curtis Akins, 51, was sitting on a bench - looking slightly exhausted -- inside a mall in Atlanta's northern suburbs as his wife looked for deals. "I think it's going to end because it's taking away from the traditional Thanksgiving," he said of the Black Friday tradition.

But that sentiment didn't stop others from taking advantage of the earlier openings and sales. "We like to shop this time of night ... We're having a ball," said Rosanne Scrom as she left the Target store in Clifton Park, N.Y., at 5 a.m. Friday.

The reception to the double-day holiday shopping start has led some retail experts to question how much further Black Friday will creep into Thanksgiving. Some now even refer to the holiday as Black Thanksgiving or Gray Thursday. "Black Friday is now Gray Friday," said Craig Johnson, president of Customer Growth Partners, a retail consultancy.

It's unclear whether or not the early openings will lead shoppers to spend more over the two days or simply spread sales between the two days. Last year, sales on Thanksgiving were $810 million last year, an increase of 55 percent from the previous year as more stores opened on the holiday, according to Chicago research firm ShopperTrak. But sales dropped 1.8 percent to $11.2 billion on Black Friday, though it still was the biggest shopping day last year.

Sales figures for this year's Thanksgiving and Black Friday will trickle out in the next couple days, but some big chains already are proclaiming early Friday morning that the start to the holiday shopping season had gotten off to a successful start.

Most Wal-Mart stores are open 24 hours, but the world's largest retailer started its holiday shopping sales events at 6 p.m. on Thanksgiving, two hours earlier than last year. Wal-Mart said that customers bought 2.8 million towels, two million TVs, 1.4 million tablets, 300,000 bicycles and 1.9 million dolls.

Rival Target, which opened at an hour earlier this year at 8 p.m. on Thanksgiving, also said that traffic starting in the early morning hours of Thanksgiving on Target.com and at its stores later in the day was "strong."

Terry Lundgren, Macy's CEO, said "so far, so good" referring to the overall holiday shopping season. The 15,000 people who showed up for the opening of the flagship store was the most ever, up from 11,000 last year.

"It's unbelievable," he said. "Clearly people are in the shopping mood."