In the image you'll see the obvious peaks on Black Friday and Cyber Monday, but you won't see the peak after Christmas for Boxing Day because this data is for the US. They have a surge in sales after Christmas, but usually not as big as the UK (You can see a similar chart for UK online only sales in an IBM report I'll discuss in a later section.).
And it looks like the UK might be following the trend shown above more anyway, because according to Barclaycard, Black Friday was the biggest...