What and who on the 21st

1913 - Arthur Wynne's "word-cross", the first crossword puzzle, is published in the New York World.

1937 - The film Snow White and the Seven Dwarfs is premiered at the Carthay Circle Theater in Los Angeles.

1962 - Rondane National Park is established as Norway's first national park. (what is it about me and Norway?)

AND I AM NOT THE ONLY ONE WHO WAS BORN ON THE 21st.:
1918 - Kurt Waldheim, Austrian United Nations Secretary-General
1937 - Jane Fonda, American actress and activist
1940 - Frank Zappa, American singer, guitarist and composer (d. 1993)
1948 - Samuel L. Jackson, American actor

and some people actually died on the 21st of december:
1807 - John Newton, English cleric and hymnist
1940 - F. Scott Fitzgerald, American writer

And yes, to finish off in perfect wikipedia style:
The December solstice, sometimes known as Yule, occurs on or very close to this date. In the Northern Hemisphere, it marks the first official day of Winter. It is also an important festival in the Chinese calendar.