 The calendar introduced by Omar Khayyám Neyshabouri, based on the classical zodiac, remains in effect in Afghanistan and Iran as the official Persian calendar.The Almagest, together with the original contributions of 9th to 10th century Persian astronomy such as the astrolabe, was introduced to Christian Europe beginning in the 11th century, by contact with Islamic Spain.Another notable Persian astrologer and astronomer was Qutb al-Din al Shirazi born in Iran, Shiraz (1236–1311).