NEW YORK — Thanksgiving could be the best day to shop all year.

An analysis of sales data and store circulars by two research firms contradicts conventional wisdom that Black Friday is when shoppers can get the most and biggest sales of the year.

Turns out, shoppers will find more discounted items in stores that are open on Thanksgiving. For example, there are a total of 86 laptops and tablets deeply discounted as door buster deals at Best Buy, Walmartand others on the holiday compared with just nine on Black Friday, according to an analysis of promotions for The Associated Press by researcher MarketTrack.

And on the Web, discounts will be deeper on the holiday. Online prices on Thanksgiving are expected to be about 24 percent cheaper compared with 23 percent on Black Friday and 20 percent on Cyber Monday, according to Adobe, which tracks data on 4,500 retail web sites.

The data is the latest proof that retailers are slowly redefining the Black Friday tradition. It’s been the biggest shopping day of the year for decades, mostly because it’s traditionally when retailers pull out their best sales events. But in the last few years, retailers like the Gap, Target and Toys R Us have started opening their stores and offering holiday discounts on Thanksgiving to better compete with online rivals.

“I was surprised, but it really shifted one day,” said Tamara Gaffney, principal analyst at Adobe, which is based in San Jose, California.

Shoppers already are noticing the deals on Thanksgiving. Corey Grassell, 34, of Appleton, Wisconsin, said he plans to shop for deals on Thanksgiving and bypass Black Friday. That’s after he grabbed bargains last year on the holiday, including a washer-dryer combination at Sears for about $800, a 50 percent discount.

“I feel guilty for going out on Thanksgiving, but the deals are so much more attractive to me than on Black Friday,” he says.  

But some industry watchers fear others won’t shop on Thanksgiving, choosing to keep the day sacred. Those who wait instead to shop on Black Friday could wind up being disappointed with the leftover deals, they say.  In fact, according to Deloitte Research’s recent survey of shoppers, about two-thirds say they’re not motivated to go out to stores Thanksgiving because it’s important to be with family and friends.   

“Shoppers could be disappointed and find that the hot items on their list are not in stock on Black Friday because of the early push by retailers,” says Traci Gregorski, MarketTrack’s vice president of marketing.

She says she’s conducting a survey of shoppers after the holiday shopping weekend to see how retailers fared. “We want to get shoppers’ perception of these deals,” she says.

Most big retailers acknowledge that they’re starting to offer deals on Thanksgiving that previously were reserved for Black Friday.

Jeff Haydock, a spokesman at Best Buy, the nation’s largest consumer electronics chain, said the best deals become available Thanksgiving when its doors open at 5 p.m. For example, one of Best Buy’s Thanksgiving specials is a $899 55-inch LED Smart TV, the lowest price it has ever offered on a Samsung ultra-high definition TV of this size.  That will be available on Friday —if supplies last.

“Naturally, more of the deals are being pulled into Thursday because our stores are open,” says Haydock.

Brian Hanover, a spokesman at Sears, which is opening at 6 p.m. Thursday, also says Thanksgiving specials spill into Black Friday. But the quantities for the 1,000 door busters are limited. They include Nordic Track treadmills for $699.99, or an $800 discount, and a 36 percent savings on a Whirlpool laundry machine, regularly priced at $549.99.

“It probably behooves the customer to shop earlier on Thanksgiving,” he says.

For its part, Walmart, the world’s largest retailer, says it’s spreading out discounts online and in the store. But Gregorski, of MarketTrack’s says its “evident” in Walmart’s circular that “the best deals are on Thanksgiving.”

To be sure, for its two sales events on Thanksgiving, Walmart devotes 36 pages of its circular to discounted TVs, computers and other items. On Black Friday? Walmart has four pages of deals.