The Middle English anonymous lyric about the labors of the months says of January
By thys fyre I warme my handys
Two of the most common (and most pleasant) “labors” for January in terms of the calendar images in books of hours are feasting (whether at a grand table like the January page from the Très Riches Heures of Jean Duc de Berry or a cozier domestic scene), and images of people warming themselves by a fire.
This detail from a January calendar page shows a man warming himself by the fire in the rondel of this January page from the Morgan Library. You’ll often see a lesser image in a margin or the base of a page or as a cutaway “exterior shot” of people playing winter sports—skating, or as in this image from the Hours of Joanna of Castile, playing ball.
Sometimes the January images contain an allusion to Janus, the Roman god of doors, with two or three heads facing in different directions, much the way January sits between the old year and the new. Another popular motif is an image of a man feasting at a table with two chalices or goblets in front of him.
Del Kolve has written about Chaucer’s Merchant’s Tale, featuring the marriage of ancient January to young and fertile May. Kolve explores the interesting calendrical echoes of images of January and of May in his Telling Images: Chaucer and the Imagery of Narrative II.