Japanese eat kabocha squash on Winter Solstice, and take a bath with floating yuzu (citrus fruit in Eastern Asia) fruit. Even though such practices are being forgotten gradually, many people still follow the custom every year.
Kabocha is often cooked with adzuki on winter solstice. Sweet mild flavor of stewed kabocha and adzuki is particularly comforting in mid winter.
If you wonder how to choose a good kabocha squash, see my previous blog entry.