Winter has gotten 30 days shorter and summer 20 days longer in Seoul over the past century.

Seoul National University Professor Kang In-shik and his team discovered the changes by studying the number of winter and summer days from 1909 through 2003.

Kang said natural seasons and the botanical environment have changed because of rapidly-rising temperatures since the 1980s.

Summer is now the longest season in Seoul, while winter was during the 1920s.