Mondays will remain - for the third year straight - the top online shopping day during the holiday season, becoming key to online shopping as weekends are to offline shopping, according to a new study from interactive technology provider Atlas, reports DM News.

"It's actually the middle of the week that's most popular the rest of the year," said Young-Bean Song, director of analytics and Atlas Institute at Atlas, Seattle, "but it switches around the holidays to Mondays. People are in the stores on the weekends, and they're fresh from the experience Monday, [and] especially at lunchtime you see sales volumes jump online."

Mondays in December are also the biggest days for search clicks: 12 percent higher than the average days.

Atlas also suggests that retailers target the workweek lunch hour. Atlas finds that consumers buy online noon to 3 p.m. EST.

In its fifth year, Atlas's study projects that Monday, December 12, is likely to generate the most e-commerce transactions, as did Monday, Dec. 13, last year - mainly due to shipping cost, with shoppers not willing to pay for express shipping by purchasing online closer to Christmas.

Atlas says retailers should also continue marketing in January. "Last year was the first year we saw January sales volume match December," Song said.