'les très riches heures de herman de vries' was inspired, conceptually, by the Très Riches Heures du Duc de Berry. The Limbourg brothers' supreme masterpiece of the genre (created between 1411 and 1416 and containing 131 exquisite miniatures) conformed to the conventional form of the book of hours, being a prayer book in which the canonical hours (horae), the Little Office of the Virgin, a calendar of months with appropriate zodiac maps and signs, etc., were elaborately illuminated and illustrated for the delectation of the very rich patron who commissioned it

[...]

de vries's heures are, conversely, those of a single summer day in 1982 spent by the artist - the experiencing subject - in the woods near Eschenau: the work consists of 131 black and white photographs taken of whatever detail of the life around him has caught his attention, a fall of sunlight through leaves, grass stems, a single leaf half-eaten by insects, foliage, the bark of a tree. Without regard to any order of devotions or any systematic relation to the passing of the hours, every exposure catches a trace of the actual light of the day on the reality of a single moment.

[source: Mel Gooding, herman de vries. chance and change (London 2006) 80-82]