Omar Khayyam in the context of "Abolhassan Sadighi"

Merv (Turkmen: Merw [ˈmeɾβ]; Persian: مرو [ˈmæɹv]), also known as the Merve Oasis, was a major Iranian city in Central Asia, located on the historical Silk Road, near today's Mary, Turkmenistan. Human settlements on the site of Merv existed from the 3rd millennium BC until the 18th century AD. It changed hands repeatedly throughout history. Under the Achaemenid Empire, it was the center of the satrapy of Margiana. It was subsequently ruled by Hellenistic Kings, Parthians, Sasanians, Arabs, Ghaznavids, Seljuqs, Khwarazmians and Timurids, among others.

Merv served as the capital of several polities throughout its history. In the beginning of the 9th century, Merv was the seat of the caliph al-Ma'mun and the capital of the entire Islamic caliphate. It served later as the seat of the Tahirid governors of Khorasan. In the 11th–12th centuries, Merv was the capital of the Great Seljuk Empire and remained so until its ultimate fall. Around this time, Merv turned into a chief centre of Islamic science and culture, attracting as well as producing renowned poets, musicians, physicians, mathematicians and astronomers. The great Persian polymath Omar Khayyam, among others, spent a number of years working at the observatory in Merv. As Persian geographer and traveller al-Istakhri wrote of Merv: "Of all the countries of Iran, these people were noted for their talents and education." Arab geographer Yaqut al-Hamawi counted as many as 10 giant libraries in Merv, including one within a major mosque that contained 12,000 volumes.

The Iranian calendars or Iranian chronologies (Persian: گاه‌شماری ایرانی, Gâh Šomâriye Irâni) are a succession of calendars created and used for over two millennia in Iran, also known as Persia. One of the longest chronological records in human history, the Iranian calendar has been modified many times for administrative purposes. The most influential person in laying the frameworks for the calendar and its precision was the 11th century Persian polymath, Omar Khayyam. The modern Iranian calendar is the Solar Hijri calendar, currently the official civil calendar in Iran.

Nowruz, the Iranian New Year, begins at the midnight nearest to the instant of the northern spring equinox, as determined by astronomic calculations for the meridian of Tehran (52.5°E). Thus the calendar is observation-based, unlike the Gregorian calendar, which is rule-based. This equinox occurs on or about 20 March of the Gregorian calendar. The time zone of Iran is Iran Standard Time, UTC+03:30.

Hasan-i Sabbah also known as Hasan I of Alamut, was a religious and military leader, founder of the Nizari Ismai'li sect, Order of Assassins, as well as the Nizari Ismaili state, ruling from 1090 to 1124 AD.

Alongside his role as a leader, Sabbah was a scholar of mathematics, most notably in geometry, as well as astronomy and philosophy, especially in epistemology. It is narrated that Hasan and the Persian polymath Omar Khayyam were close friends since their student years. He and each of the later Order of Assassins' leaders came to be known in the West as the Old Man of the Mountain, a name given by Marco Polo that referenced the sect's possession of the commanding mountain fortress of Alamut Castle.