Final answer:
On the cosmic calendar, the Big Bang occurred at the beginning of January 1st, with our solar system forming on September 10th, and humans emerging in the final hours of December 31st.
Step-by-step explanation:
The Big Bang according to the cosmic calendar occurred at the very start of January 1st if we compress the entire 13.8 billion year history of the universe into one year for better conceptual understanding. On this scale, significant events such as the formation of our solar system took place around September 10th.
Another critical moment, the time when the universe cooled enough for atoms to form, happened about 380,000 years after the Big Bang, which would be represented very early in the cosmic year. The emergence of creatures we would recognize as human only appears in the last hours of December 31st on this cosmic calendar.