[Appears in med.L. as almanac(h in end of 13th c., and soon after (though it may have been earlier) in most of the Rom. langs., It. almanacco, Sp. almanaque, Fr. almanach, the immediate source of which was app. a Spanish Arabic al-mankh; Pedro de Alcala, in his Arabic-Castilian Vocabulista (1505), has ‘mankh, almanaque, calendario’; also ‘mana (probably meant for same word), relox del sol’ [sundial]. But the word occurs nowhere else as Arabic, has no etymon in the language, and its origin is uncertain. See note at end of this article.] 

    An annual table, or (more usually) a book of tables, containing a calendar of months and days, with astronomical data and calculations, ecclesiastical and other anniversaries, besides other useful information, and, in former days, astrological and astrometeorological forecasts.
  (The ‘almanacs’ known to Roger Bacon and Chaucer were permanent tables of the apparent motions and positions of sun, moon, and (?) planets, whence the astronomical data for any year could be calculated. ‘The calculations [of Regiomontanus, 1475] of the places of the sun and moon were the best that had been made in Europe..He speaks of them himself as “quas vulgo vocant almanach”’ (Hallam Lit. Eur. 1855 I. 190). In 15th c. almanacs or ephemerides began to be prepared for definite periods, as 30 or 10 years, and in 16th c. for the year, with which was combined the ecclesiastical calendar; astrological and weather predictions appear in 16-17th c.; the ‘useful statistics’ are a modern feature.)