We are able to estimate quite easily how long this drudgery might have taken, because two of the four volumes contain their dates of completion: 23 December 1449 in volume 3 and 1 July 1450 in volume 4. In other words, the transcription of each volume took six months, which means that on the basis of 250 working days a year, the scribe would have three to four pages each day. He began this work in mid-1448, at the start of the term of office of Nicaise de Frasne (1447–1461), an abbot who had close ties with the Duke of Burgundy Philip the Good.
The four volumes of the Geraardsbergen Breviary were copied out entirely by hand by a scribe or copyist, a craftsman whose specialism was writing.
To bring a commission on such a scale to a successful conclusion, the work would often be shared among several copyists. However, that did not happen in this case. The writing is clearly the work of one hand alone. We even know the name of that person, because he has left us his signature: Wilhelmus de Predio. We know nothing about his background and education, but we do know something about him as it was not only the Geraardsbergen Breviary that he signed.