The Persian year begins in the vernal equinox: if the astronomical vernal equinox comes before noon, then the present day is the first day of the Persian year.
If the equinox falls after noon, then the next day is the official first day of the Persian year.
Thus an eclectic cultural elasticity has been said to be one of the key defining characteristics of the Persian spirit and a clue to its historical longevity.
Furthermore, Iran's culture has manifested itself in several facets throughout the history of Iran as well as the Caucasus, Central Asia, Anatolia, and Mesopotamia.
Farhang-e Irān), also known as culture of Persia, is one of the oldest in the world.
Owing to its dominant geo-political position and culture in the world, Iran has directly influenced cultures and peoples as far away as Italy, Macedonia, and Greece to the West, Russia to the North, the Arabian Peninsula to the South, and South and East Asia to the East.
The article uses the words Persian and Iranian interchangeably, sometimes referring to the language and its speakers, and other times referring to the name of pre-20th century Iran, a nomenclature which survives from western explorers and orientalists.