Used as a prayerbook as well as a book of hymns for church services, the psalter in the later middle ages was often produced with a calendar and additional prayers. Eventually it was combined with an abridged version of the breviary, the prayerbook used by monks, to form the special lay prayerbook, the book of hours. This psalter represents an important stage in this development as it took place in England. It is one of the earliest psalters to include the Hours of the Virgin, a special set of devotions taken from the breviary. Also it is the earliest of a line of richly decorated psalters which were probably made at Oxford, in the workshops by lay scribes and artists, an industry which grew out of book production for the university. Many later medieval psalters included a calendar to alert the reader to feast days, on which they could say special prayers. Calendars developed a standard set of images for their decoration. Here, for February, a typical image of the winter weather, a man wrapped in a blanket and warming his feet by the fire. Below is Pisces, the sign of the zodiac for late February, noted in red, 'Sun in Pisces.' The feasts of the purification of the Virgin and the dedication of the cathedral of St Peter are highlighted in blue, while a feast of St Matthew is in red (a 'red-letter day').