Ok then it is 4 weeks for both January and February. But I still don't see why in average, people estimate +10-15% for Feb compared to Jan.
The PS4 and XBO have averaged 70% higher sales in February than in January so far. That's why. People start getting their tax returns, and spend them on big ticket items like game consoles. There are rare occasions where January is as big as February, but the norm is for January to be by far the weakest month of Q1.