Dionysius Exiguus composed the earliest known computistical formulary written in Latin in 525. However, this formulary has not survived in its original form. The editors of Dionysius’ computistical writings, Wilhelm Jan and Bruno Krusch, published a corpus of 16 argumenta from a single manuscript, namely MS Oxford, Bodleian Library, Digby 63 under Dionysius’ name, since this was the only manuscript known to them that preserved the original 525 dating. Some of these 16 argumenta, however, contain dating clauses as late as 675, which immediately cast doubt on their ascription to Dionysius. In fact, the 16 argumenta edited by Jan and Krusch should more precisely be defined as a computistical formulary of 675, to be termed the Computus Digbaeanus of 675, which includes the original Dionysiac argumenta. This article, then, reconstructs the original Dionysiac corpus on the basis of new manuscript evidence. Moreover, the different stages of interpolations and additions that eventually led to the composition of the Computus Digbaeanus are analyzed, and with this the development of computistical formularies written in Latin in the 150 years from 525 to 675.