This is a manuscript copy of Kitāb al-Azmān (The book of times; also known as Kitāb al-Azmina) by Yuḥannā Ibn Māsawayh (died circa 857), the famous physician of the Abbasid era. The work belongs to the tradition of Islamic hemerology—the study of the calendar, especially with a view to discerning the auspiciousness of carrying out various actions at a given date or time. In his introduction, the author states: "The people of knowledge and philosophy and the physicians of Persia, India, and Rūm [Asia Minor], have said that the year is divisible into four sections: spring, summer, fall, [and] winter. They then designated for each of these sections that which pertains to it as far as zodiacal signs, and these are three, and [they designated for each as well] the stations of the moon (al-anwāʾ), and these are seven. And they expressed for each of their constituent parts the actions that are opportune in being carried out." What follows is a section on each season, listing the number of days, the zodiacal signs, the stations of the moon, and the Galenic humor associated with each season, along with the appropriate pairing of the qualities of hotness, dryness, coldness, and moistness. In the section on winter we read, for example, that it resembles "water, for it is cold and wet, and in this season coughing is evoked as well as pleurisy." A longer section follows, listing al-shuhūr al-rūmīya (the Roman months) in their Levantine forms, giving more detail about the significance and the customary practices of each day. The entry for Tishrīn al-awwal (October), for instance, states that on its first day the east wind commences to blow and that people descend from the roofs, and that the tenth day of the month is the day on which Abraham set off with his son to sacrifice him. Ibn Māsawayh states that one should minimize sexual intercourse in this month and avoid the eating of watermelons and cucumbers and cream and the flesh of cows as well as grains other than rice. He also proscribes the drinking of cold water in this month. The colophon for the current manuscript does not include a date but it lists the scribe's name as Ṣāliḥ Salīm ibn Salīm ibn Sa‘īd al-Shāmī al-Dimashqī. This copy is inscribed on the cover with the words Maktabat Taymūr (the library of Taymūr). A partially legible seal impression contains the name Taymūr and the date 1912, indicating that this manuscript was bequeathed to the Dār al-Kutub (National Library of Egypt) by the Egyptian Kurdish scholar and humanist Ahmad Taymūr (1871–1930.).