The day after Christmas is the start of the biggest week for holiday gift returns and a tough time for retailers. - 

You’ve heard of Black Friday. It’s the day after Thanksgiving, and it’s when retailers ring up big sales as people shop for the holidays. Black Friday sales get a lot of attention, but the real chaos comes after Christmas.  

“In a lot of ways, it's the same kind of craziness and energy that is there around Thanksgiving,” says Sucharita Mulpuru, a retail analyst at Forrester. There’s the after Christmas sales and the throngs of people making returns. Mulpuru says that about 15 percent of holiday gifts don’t make the cut.

“Typically, one of two things happen," she says. "If it’s a gift receipt you get a gift card that is the value of the item."  

And if you don’t have a receipt, you can make an exchange. Either way the process is more time consuming than a straight sale. Mulpuru says retailers put their more experienced workers on returns, and between Christmas and New Years they open more terminals to handle them.

Retailers like Walmart are extending their return and exchange period.

“Standing in line and returning gifts you want to make that as easy as possible especially the day after Christmas," says Sarah Spencer, a spokeswoman for Walmart.

Generally, the holiday return/exchange period is limited to 15 to 30 days. But Walmart says for purchases made between Nov. 1 and Dec. 24, they'll start the clock on December 26.

That way people are less likely to go away unhappy and more likely to use their gift cards or make exchanges that same day.