I think that it's horse-hockey. They are counting the days between Thanksgiving and Christmas, which were as few this year as they ever get. And to exclude on-line sales makes it even more horse-hockey.
Regardless of the number of shopping days, relatively few consumers start their shopping until after Thanksgiving. Many put it off as long as possible because they have been trained that deals are going to happen if you only wait long enough. People are not going to do their Xmas shopping in January, except perhaps for themselves. Thus regardless of the number of days available, the shopping has to occur withint that period or be lost. The number of days is ONLY relevent in that it defines how much pressure the stores are under to meet their goals. Its not like fast food where the number of meals is proportional to the number of days. The number of people shopped for and the amount spent should be the same regardless of how few days you have to do the shopping in. I didnt start until the weekend before Xmas.