Another Cosmic Calendar event already!
Only the day after the Solar System begins to form, our own humble planet comes into being.
(Remember, because we are compressing the entire history of the cosmos into one year, each day represents 37.4 million years.*)
I apologize for not having more to say just now - I am still in PhD write-up mode.
 Wikipedia, as usual.
 Talk Origins page on dating the age of the Earth
* For those who have followed this series from the beginning, you might remember that I claimed before the each day is 41 million years. I am now calling it 37.4 million. What gives? The earlier figure was based on a 15 billion-year-old universe. I have since learned that the consensus is for a slightly younger universe, at 13.7 billion years. Remember, this is a calendar based on what we know, and so when what we know changes, so does the calendar. If anyone else wants to fact-check my figures and calculations, please let me know.