Retailers and online shopping sites will be all the buzz this week, considered the busiest shopping time of the year - but it really may not be, according to a MasterCard study.

Two of the busiest shopping days of the year, "Black Friday" and "Cyber-Monday," will kick off the frenzy of online and offline shopping that will carry forward until Christmas, InternetNews writes. The holiday shopping season is pivotal for e-commerce sites, as CoreMetrics claims that most retailers generate 20-40 percent of their annual e-commerce revenues and profits during the holiday season.

And yet, "Black Friday", or the day after Thanksgiving, and "Cyber-Monday", the Monday after Thanksgiving, aren't as popular for shoppers as many think. A new study by MasterCard Worldwide claims that neither day ranks within the Top 5 busiest shopping days, Reuters reports.

The MasterCard study found that more and more consumers are putting off the majority of their Christmas shopping until the final week, and predicts that Dec. 23 will be the busiest shopping day of the year. The study also found that Cyber-Monday wasn't the busiest online shopping day last year; Dec. 5 was.

Most shoppers, either online or offline, will use plastic to pay for their transactions: 35 percent of those surveyed said they will use debit cards most often for holiday shopping, and 33 percent said they plan to use credit cards. Only 12 percent said they will use cash to pay for most holiday purchases, and 6 percent plan to use personal checks.