The term refers to iconographic cycles in medieval and early Renaissance art depicting the agricultural and domestic activities associated with the twelve months of the year. The labors of the months are often found as elements of sculptural decoration in churches (especially on the archivolts of portals), in illuminated manuscripts (especially in books of hours), and in stained glass windows. Labors of the months cycles varied with the date, location, and the purpose of the work, but a typical cycle would be: January: feasting; February: warming by the fire or planting; March: pruning trees; April: celebrating Spring or picking flowers; May: hawking or courting; June: haymaking or sheep-shearing; July: harvesting wheat; August: threshing; September: harvesting grapes or winemaking; October: plowing or sowing; November: gathering acorns for swine; December: slaughtering hogs. Web resources here and here.

Jean Colombe. September (det.), from the Très Riches Heures du Duc de Berry. Watercolor with gum Arabic binder on parchment. Ca. 1485–1489. Musée Condé, Chantilly, France, MS 65.