If the entire history of the universe fit into one year. When did you show up?
If you compress the entire history of the universe into one calendar year, the Big Bang happens at midnight on January 1. The Milky Way galaxy forms around March. The Solar System forms around September 2. Life on Earth appears shortly after — but everything interesting happens in the last few days.
Dinosaurs appear on December 25. They go extinct on December 30. Homo sapiens — modern humans — appear at 11:48 PM on December 31. All of recorded history fits into the last 14 seconds of December 31. Every king, every war, every invention, every poem — 14 seconds.
This is how Carl Sagan originally visualized deep time. It's not that human history is important. It's that human history is so short, compared to the age of the universe, that it's barely a blip. The Earth has been here for 4.5 billion years. We've been recording things for about 5,000. That's 0.0001% of Earth's history. We just got here.
Carl Sagan, in his 1980 TV series Cosmos. He compressed 13.8 billion years into one calendar year to make deep time understandable. It's been used in classrooms ever since.
December 31, 11:48 PM. All of recorded history fits into the last 14 seconds. The Pyramids, the Roman Empire, the Renaissance, World War II — all in 14 seconds.
December 31, around midnight. The Sun becomes a red giant in about 5 billion years, which is December 31 on the cosmic calendar. That's the end of the year for us.
This is Carl Sagan's famous Cosmic Calendar. It compresses the 13.8-billion-year history of the universe into a single 365-day year. The Big Bang happens on January 1st at midnight. Present day is December 31st at midnight.
The first stars don't ignite until late January. Complex life doesn't appear until August. Dinosaurs go extinct on December 30th. And humans? We don't show up until 11:48 PM on December 31st. All of recorded history fits into the last 14 seconds.