It may seem strange that in some of the documents with the double-dates the second figure is given as eighteen and in others as nineteen. There is more than one way in which it is possible to explain the discrepancy. If we assume that the conquest of Nîsin took place towards the close of Rîm-Sin's seventeenth year, it is possible that, during the two years that followed, alternative methods of reckoning were in vogue, some scribes regarding the close of the seventeenth year as the first year of the new epoch, others beginning the new method of time-reckoning with the first day of the following Nisan. Rut that explanation can hardly be regarded as probable, for, in view of the importance attached to the conquest, the promulgation of the new era commemorating the event would have been carried out with more than ordinary ceremonial, and the date of its adoption would not have been left to the calculation of individual scribes. It is far more likely that the explanation is to be sought in the second figure of the equation, the discrepancy being due to alternative methods of reckoning Rîm-Sin's regnal years. Again assuming that the conquest took place in Rîm-Sin's seventeenth year, those scribes who counted the years from his first date-formula would have made the second year of the era the eighteenth of his reign. But others may have included in their total the year of Rîm-Sin's accession to the throne, and that would account for their regarding the same year as the nineteenth according to the abolished system of reckoning.[23] This seems the preferable explanation of the two, but it will be noticed that, on either alternative, we must regard the first year of the Nîsin era as corresponding to the seventeenth year of Rîm-Sin's reign.