As retailers continue to extend Black Friday shopping hours, one company who has always had hours on Thanksgiving Day recently sparked outrage from customers.

Kmart came under fire after announcing on Nov. 5 that they would open at 6 a.m. on Thanksgiving Day and stay open for 41 hours straight through Black Friday. The retailer previously would open early Thanksgiving Day, but then close at 4 p.m. to allow employees time with their families on Thanksgiving before re-opening again on Black Friday at 6 a.m.

The new hours have customers on social media threatening to boycott Kmart stores, reportedly calling the company "heartless," "Greedy," "shameful" and "disgusting" for not giving its workers time off to spend with their families.

"WOW! Kmart is opening their doors at 6am on Thanksgiving? Way to go Kmart! Thankd for showing us you don't give a damn about your people," Elizabeth Gmaz tweeted.

Some took to Facebook to express their outrage, posting messages to the company's page saying the retailer should be ashamed of itself.

"You have lost my business, not just for the holiday, but always," Laurie Lambert wrote.

"Kmart, you are destroying families. Making people work and taunt people to shop on Thanksgiving. I have chosen NOT to shop at K-mart for these sales. You are making me sick," Mary Jane Czemerda said.

Traditionally, Black Friday is considered the first day of the traditional holiday shopping season. Years ago, retailers would open earlier the day after Thanksgiving and offer steep discounts on popular items to lure shoppers in. As the years have gone on however, stores have opened increasingly earlier, and several now open on Thanksgiving Day.

Other stores that have already announced that they would be opening for Black Friday shoppers on Thanksgiving Day include Macy's, J.C. Penney Sears and Kohls, who have all announced 8 p.m. openings, and Toys 'R Us, which will be opening at 5 p.m. this year. The two other biggest discount retailers, Target and Wal-Mart, have yet to publicly announce their opening times.

K-Mart has responded to some of the backlash online, saying they would staff stores with volunteers and seasonal associates whenever possible, and further defended their decision by saying "This gives associates the opportunity to make some additional money this holiday season."