Macy's plans to open its doors at 6 p.m. on Thanksgiving, six hours before traditional Black Friday shopping officially begins. It's the earliest Macy's has ever opened for the holiday shopping frenzy.

The department store chain used to open at midnight the day after Thanksgiving, similar to most retailers, including Walmart. But stores have been opening their doors earlier. 

This holiday season, retailers are hoping to cash in on a three-year shopping high. The National Retail Federation projects that retail sales will grow an annual 4.1 percent this season, to nearly $617 billion. 

Last year, Macy's began Black Friday deals in stores at 8 p.m. on Thanksgiving. 

The employees working on the holiday have all volunteered for the shift and are compensated with "incentive pay," the company said.

"We work diligently to staff Thanksgiving with associates who volunteer to work, and doing so means that our people are able to make their own decisions about how they contribute to our most important and busiest weekend of the year," Macy's said in a statement. "We also heard last year from many associates who appreciated the opportunity to work on Thanksgiving so they could have time off on Black Friday."