A U.S. Postal Service (U.S.P.S.) worker unpacks packages from a truck on December 02, 2019 in San Francisco, California.

The holiday shopping season is a crucial period for retailers and can account for up to 40% of annual sales. But this year, Thanksgiving, which traditionally starts the U.S. holiday shopping period, was on Nov. 28, a week later than last year's Nov. 22, leaving retailers with six fewer days to drive sales between Thanksgiving and Christmas.

U.S. shoppers spent more online during this year's holiday shopping season, a report by Mastercard showed on Wednesday, with e-commerce sales hitting a record high.

E-commerce sales this year made up 14.6% of total retail and rose 18.8% from the 2018 period, according to Mastercard's data tracking retail sales from Nov. 1 through Christmas Eve.

Overall holiday retail sales, excluding autos, rose 3.4%.

"E-commerce sales hit a record high this year with more people doing their holiday shopping online," said Steve Sadove, senior adviser for Mastercard.

"Due to a later than usual Thanksgiving holiday, we saw retailers offering omnichannel sales earlier in the season, meeting consumers demand for the best deals across all channels and devices, Sadove said.

The last shortened shopping season was in 2013, when retail chains and delivery companies scrambled to get packages to shoppers in time for Christmas.

Since then, retailers have invested heavily to provide same-day delivery, lockers for store pick-up and improve their online presence as they battle against retail giant Amazon.com Inc for market share.

Consumers also benefited from a low unemployment rate and rising wages, even as global uncertainty and trade tensions have hit business investment.

The data showed sales at department stores fell 1.8% and online sales growth of 6.9%, emphasizing the importance of click-and-collect and online ordering.

The apparel category registered stronger-than-expected e-commerce growth, Mastercards data showed, with online sales rising 17%.