An almanac (also spelled almanack and almanach) is a regularly published listing of a set of current information about one or multiple subjects. It includes information like weather forecasts, farmers' planting dates, tide tables, and other tabular data often arranged according to the calendar. Celestial figures and various statistics are found in almanacs, such as the rising and setting times of the Sun and Moon, dates of eclipses, hours of high and low tides, and religious festivals. The set of events noted in an almanac may be tailored for a specific group of readers, such as farmers, sailors, or astronomers.
The etymology of the word is unclear. The earliest documented use of the word in something like its current sense is in Latin in 1267. Roger Bacon used it to mean a set of tables detailing movements of heavenly bodies including the Moon.
It has been suggested that the word almanac derives from a Greek word meaning calendar. However, that word appears only once in antiquity, by Eusebius who quotes Porphyry as to the Coptic Egyptian use of astrological charts (almenichiaká). The earliest almanacs were calendars that included agricultural, astronomical, or meteorological data. But it is highly unlikely Roger Bacon received the word from this etymology: "Notwithstanding the suggestive sound and use of this word (of which however the real form is very uncertain), the difficulties of connecting it historically either with the Spanish Arabic manākh, or with Medieval Latin almanach without Arabic intermediation, seem insurmountable."
One etymology report says "The ultimate source of the word is obscure. Its first syllable, al-, and its general relevance to medieval science and technology, strongly suggest an Arabic origin, but no convincing candidate has been found". Ernest Weekley similarly states of almanac: "First seen in Roger Bacon. Apparently from Spanish Arabic, al-manakh, but this is not an Arabic word....The word remains a puzzle." Walter William Skeat concludes that the construction of an Arabic origin is "not satisfactory".