According to Official Guinness Records,
Longest literary gestation
The standard German dictionary Deutsches W”rterbuch was begun by the brothers Grimm (Jacob and Wilhelm, 1785-1863 and 1786-1859 respectively) in 1854 and finished in 1971 and consists of 34,519 pages and 33 volumes.
In 1629, the ecclesiastical historian Jean Bolland (1596-1665) began a chronicle of saints' lives called Acta Sanctorum, following an original idea by the priest H‚ribert Rosweyde. It was arranged according the saints' feast days;during his lifetime Bolland completed the first two parts, January and February. The work was later taken up by a group of Belgian Jesuits known as Bollandists, and additions were made periodically over the next three centuries. An introduction for December was published in 1940, and there are now 67 folio volumes of the completed Acta Sanctorum.
Oxford University Press received back their proofs of Constable's Presentments from the Dugdale Society in December 1984. They had been sent out for correction 35 years earlier in December 1949.
For a complete list of Unknown date records, please visit Unknown date Guinness Records in Germany.