Ancient people of the Earth, migrated North out of Africa 20,000 years go, in search of water. Survival was key. That struggle for existence made people appreciate being alive, with every breath they took. Living in "the now" became a holy exercise.
As they marched North, they found water in the foothills of the Zagros mountains, in the Iranian plateau. Due to the geographical position of the Iranian plateau, four seasons exist in this part of Earth. And so for the first time, the humans in the Iranian plateau developed an acute sense of measurement.
Time and space was measured, for the first time in the history of mankind. They began to grow food for the first time. The use of the land was sacred. Ancient Iranians valued land and believed in heaven on Earth.
Many humans marched even further North to Europe. Many stone circles were created, to measure the change in the seasons. Ancient calendars were created according to movement of the Moon, Sun and many different planets.
There is to date no calendar system, that is as accurate as the Iranian calendar, because it begins at the only time; when the Earth is vertical against the light of the Sun; the light is equally distributed on Earth, and the Sun rises through the Equator. Just read this article on Equinox at Wikipedia:
This mathematical and astronomical basis, has stood the test of time. In Iran, Persepolis was placed at the center of the world, being equidistant from the most Eastern and Western lands on Earth. Read this article which depicting later day Nimrooz that is also very close in latitude to Persepolis.
But I have my own sense of duty to share. Some thirty years ago, I realized that a lot of our ancient belief has been stripped off its philosophy, as well as its science. At the Spring festival, what we had, was a gathering around the Koran, on a bunch of things on a tray, that started with the S sound. No one cared, or was curious, to find out more. No one really knew what Hafseen meant. "Oh Ali, it is just Spring, forget all that history and astrology". I would hit back.
The Shi'ite revolution against Iran, produced a backlash. There were those who hated Islam and those who were atheists. A force that said, “Share the ancient spirit”, motivated me. I spent endless nights in the Firestone Library doing serious soul searching. I was not happy, with was being done to an ancient heritage. I forgot my normal curriculum and had to leave Princeton for a year. But it was worth it. I found my identity and purpose. My existence. I studied history of time and graduated as a Geologist. No one had looked, at an Astrological or Cosmological analysis, of what was labeled as Zoroastrianism. Very few people in the 70's, let alone the 60's or earlier, had heard of the Zend-Avesta. No one connected Zend-Avesta to Astrology.
Everyone had heard of the Shahnameh. Ferdowsi felt that Iran needed a revival of existence. But even today, most people do not know that Shahnameh is a poor copy of an older book called Khodayeh Namak; written the last time Iranians did some soul searching, and wrote the history of Iran in the Sassanian Era.
Again the Shahnameh was just a long list of the Royal families of Iran. Very little is written about the philosophy or cosmology. This form of existence became the Shah's undoing, as it rallied the Muslims and Communists. It was written without one word of Arabic. But we now know, that there is an older language, common to all languages, called Proto-Elamite.
Suddenly the Iranian plateau was the root of world's culture. Anti-Arab xenophobia was not necessary. We have country full of archeological monuments that no one could explain. The Muslims and communists wanted to flatten them all, even though Salman created Islam and Mazdak created Communism. It all became so divisive.
For years, I heard so many archaeologists describe Persepolis, but no one knows why the Lion is biting the Bull so prominently in Persepolis. If you look at the Wiki article, you will see that the Equinoxes have changed sign almost every 2000 years. It is called the precession of the Equinox. There is a specific time when it happens. It is a point of existence. A point that is not divisive. The ancient world decided to build Persepolis the moment the Vernal Equinox as represented by the Sun (Lion), moved from Taurus or Ordibehesht to Farvardin or Aries in 1865 BC. This is also, when age of Aryans and the right to self-determination, began. Human rights was given to all. Every form of existence could be tolerated.
We are told that Zoroaster's birthday is 3780 years ago, and he became enlightened at the age of 30 upon his first Saturn return. So the adopted Zoroastrian calendar is now 3751. But I think he was born in 1865 BC and became enlightened 1835 BC, so the year now should be 3847. These dates vary so much. The royalists take it from Declaration of Human Rights from 559 BC. The Shi'ites start from 642 AD.
I think, the ancient Iranians, wanted a message to survive across time. The Age of the Bull had ended in 1865 BC and the age of the Sun exalted in Aries had begun. That is why we have that engraving on Persepolis. There is a specific time of the year, when the light shines through Persepolis, that tells us the exact time of the Spring Equinox. To encapsulate that moment of the new Age of Aries, the soldiers of the walls of Persepolis are mirror images of each other. We respect the seven most important concepts, Earth, Fire, Water, Air Human, Plant, and Animals. Each has an Ameshasepanta or a Guardian Angel. The S sound comes from Sepanta. Modern Iranians have found, that our ancestors wanted to feel alive, by appreciating nature's energies. It did not matter what politics or religion was ruling Iran. We all existed as Iranians by existing with Knowrooz. Nothing can take that family ritual away. It unites and it is not controversial. And if you are alone in a foreign country, you can explain the good reason for celebrating Spring as the beginning of the year, and everyone will be envious, for having such an old ritual that still exists, after all these years.