The planarii rarely provide the dates of benefaction. These have to be found from other sources, which are scarce before the fourteenth century. For the later fourteenth and fifteenth centuries, dating is made easier through charter evidence, and poor-table and parish records (for Our Lady's and St Saviour's). The chapter act-books of St Donatian's register larger foundations.

The oldest surviving planarius of St Saviour's is dateable to the early 1340s, after which names were added in later hands until the late fifteenth century. This dating can be established as follows. Some forty-five names of benefactors written down in the first hand can be identified: all belong to the period c. 1231 to 1336. All the names that appear after the 1340s were written down by later hands. The frequently appearing names of Gerard Sox and Bernard Priem, whose foundations can be dated to c. 1342, were written down sometimes in the same older hand, sometimes in a later one. The name of Jan de Burgrave (whose obit can be dated to 1343) was entered by the older hand. The name of Agnes de Boneem (whose extensive foundations can be dated to between 1344 and 1351), was added slightly later. Additional material can be found in the sixteenth-century planarius. It seems that the first planarius was not added to much beyond 1490: there are a number of obits that can be dated to the 1480s, but very few after then.