On Carl Sagan’s Cosmic Calendar (illustrated as a comic strip here), which maps the entire history of our cosmos onto a single year, September is particularly interesting.
Since the Big Bang in January (13.7 bya or billion years ago), the universe has been gradually increasing in organizational complexity. Little of local significance has occurred, though, apart from the formation of the Milky Way galaxy in May.
Now, in September, a good three-fourths of the way through the story, our little corner of the cosmos gets interesting. On the 1st (4.57 bya), our own sun emerges.