The Cosmic Calendar Tells You The History of the Universe

the cosmic calendar

The average human lifespan worldwide is 71.4 years. The average lifespan by gender is 71 years and 8 months for females and 68 years and 4 months for males, according the United Nations World Population Prospects 2015 Revision.

Since we live for such a short time, it can be hard to wrap our head around the time intervals between events in the history of the universe.

The Cosmic Calendar helps us realize the huge amount of time between each event by compressing the entire history of the universe into only one year.

The Cosmic Calendar was introduced by the famous astronomer Carl Sagan in his book: The Dragons of Eden (1997), and on his television show “Cosmos”.

The Cosmic Calendar


The first event in the universe’s history was its creation, which happened on the very first second of January 1st. The universe expanded and cooled. On January 10th, the first stars were formed.

These stars came together to form the first small galaxies on January 22nd.


On May 1st, the Milky Way Galaxy was formed.

We know this because the oldest stars in our galaxy are this old. The Milky Way was formed by slowly consuming smaller galaxies, so not all the stars are the same age.


In early September, on the 9th, the sun was born. This is the beginning of the formation of the Solar System.

Five days after the sun’s birth, on the 14th of September, the earth comes to existence (note that a day in the cosmic calendar is almost 40 million years, but we’ll go into that later).

On September 25th, something big happens. The first life begins on Earth! It starts as the simple, single cells, and they learn photosynthesis nine days later, on September 30th.


On the 15th, the first complex cells appear.


December is a busy month in the cosmic year.

First, on the 5th of December, the first multicellular life begins.

Then, on the 7th, fish are formed. Soon after, plants, insects, and seeds come into existence, on the 20th and the 21st.

Dinosaurs follow, showing up on earth on the 25th.

Notice how the year’s almost over, but humans still don’t exist. Don’t worry, we’re coming.

A day after the dinosaurs, mammals come to be. One more day, and we have birds.

On the 28th, we become the most beautiful planet when the first ever flower blooms. Things are looking good on earth. It seems like a good time for humans to turn up.

On the 31st of December, the last day of the year, at 6:30 am, an asteroid hits earth, destroying the reptiles that have been ruling earth for the last five days and making way for a ruler.

Hours later, at ~10:30 pm, primitive humans come into being. Within the next hour, we make and use stone tools and fire.

At 11:52 pm, modern humans come along.

11:58 pm is when seafarers settle in Australia.

By ~11:59 pm, there’s already extensive cave painting in Europe. It takes us twenty seconds after that to invent agriculture.

The Egyptians develop astronomy at 11:59:50 pm.

Buddha is born at 11:59:55 pm, and Christ is born one second later at 11:59:56 pm.

Muslim conquests take place at 11:59:57 pm. The Mongol invasion happens one second later. Wait another second, and you have the Renaissance in Europe.

Everything that happened in the last 400 years: walking on the moon, the invention of cars and planes, and the World Wars, all happened in the last second of the Cosmic Calendar year.

All recorded history happens in the last 10 seconds of the year.

Or as deGrasse Tyson put it:

Every person you’ve ever heard of lies right in there. All those kings and battles, migrations and inventions, wars and loves, everything in the history books happened here in the last seconds of the cosmic calendar.

How Much is Time Compressed?

The Cosmic Calendar squeezes 13.8 billion years into just one. So 1 second is worth much more time in the Cosmic Calendar, but by how much?

1 second in the cosmic calendar equals 475 years. Each hour is equal to 1.7 million years, and each day equals 37.8 million years.

24 days in this calendar equal a billion years in real time.

As time goes on and more events occur, the Cosmic Calendar will just compress more and more.