This is a calendar that puts the entire history of the universe into one calendar year.
The universe has been around for 13.8 billion years. In the grand scheme of things, this means that human life has only been around for the blink of an eye. When 13.8 billion years is put into one calendar year, homo erectus does not appear until 10:48 pm on December 31. All of our human history is packed into the last few hours and minutes of the last day of the year. For most of the universe’s history, humans weren’t even on the radar. On the Cosmic Calendar, Christopher Columbus’ voyage to America happened one second before midnight. All of America’s history, the founding of the United States, our independence from Britain, happened in less than one second. All of industrialization and technology and human development that has lead to the Earth’s surface and climate changes have happened in the blink of an eye. It is disconcerting to think that the Earth was around for billions of years with no humans, and in the time that humans have inhabited the Earth, we have greatly impacted the climate like nothing ever has before. The concept of the sheer vastness of time that the Universe has been around makes human life and society seem insignificant, yet we have had very significant effects on the health of our home planet. Hopefully, we can reverse our detrimental effects and minimize our damage to the Earth to keep it proportional to the amount of time we have been around.
Holly's Astronomy Blog 
The Cosmic Calendar is one of my favorite topics and I’m so glad you decided to contemplate it further! It amazes me to think about how long the dinosaurs were here! And how short of a time we humans have been here!
So I found a worksheet about the cosmic calendar (http://www.astrosociety.org/edu/astro/act2/H2_Cosmic_Calendar.pdf) and I think one of my favorite things about this one as opposed to the awesomely colored one from our book is that it has a calendar that says how many days before the new year that was, and I think it’s really interesting to think about how many days ago things happened. Not just when they happened on the calendar in general, which already makes them seem close, but it’s especially close when you put it into numbers. Two days ago and four days ago seem really close said that way.
I agree with you that it is unsettling to think about how much humans have impacted Earth is the very short time we have been around compared to how long the Earth has existed. On the Cosmic Calendar, dinosaurs were on Earth for around 6 days and humans have been on Earth less than 2 hours (our technologies for even less time than that), yet we have changed the planet in significant ways. It makes me think about how long humans will survive on Earth, and if the amount of time will even be a whole day on the Cosmic Calendar.
Your point that we’ve only been around for a blink of an eye, and yet we seem to have impacted the climate immensely is very interesting. To think that earth has been around for billions of years without intelligent life is crazy! It really puts our place in the universe into perspective. The life of a human is nothing compared to the vast history and future of space. Also, the fact that we have been able to impact our planet so much over so little time is quite disconcerting. I definitely agree that it’s our responsibility to reverse the damage we have caused our planet. Hopefully we can correct it as quickly as we caused it!