According to popular tradition, they fall between 29th and 31st January. 

They are thought to be the coldest days of the year, and are tightly connected to an Italian legend.

 

The blackbird, which once had a white plumage, went to take shelter inside a chimney for warmth and refuge from cold. This caused its coat to turn black, because of the soot found there.

From that day on, this bird remained that colour.

 

Moreover, the legend has it that if these days are cold, spring will be warm and beautiful. On the other hand, if they’re warm, spring will come later.