Conversation so far:
What day was Isaac Asimov born on?
Isaac Asimov was born in Petrovichi, Smolensk Oblast, Russian SFSR on an unknown date between October 4, 1919 and January 2, 1920.
What is the closest date to Isaac Asimov's birthday?
01/02/1920

Question: What day did he choose
Self-contained rewrite: What day did Isaac Asimov choose?