It is at this point that a further discovery of Prof. Clay has furnished us with the necessary data for a decision. Among the tablets of the Yale Babylonian Collection he has come across several documents of Rîm-Sin's reign, which bear a double-date. In every case the first half of the double-date corresponds to the usual formula for the second year of the Nîsin era. On two of them the second half of the date-formula equates that year with the eighteenth of some other era, while on two others the same year is equated with the nineteenth year.[20] It is obvious that we here have scribes dating documents according to a new era, and explaining that that year corresponds to the eighteenth (or nineteenth) of one with which they had been familiar, and which the new method of time-reckoning was probably intended to displace. Now we know that, before the capture of Nîsin, the scribes in cities under Rîm-Sin's control had been in the habit of dating documents by events in his reign, according to the usual practice of early Babylonian kings.[21] But this method was given up after the capture of Nîsin, and for at least thirty-one years after that event the era of Nîsin was in vogue.[22] In the second year of the era, when the new method of dating had just been settled, it would have been natural for the scribes to add a note explaining the relationship of the new era to the old. But, as the old changing formulæ had been discontinued, the only possible way to make the equation would have been to reckon the number of years Rîm-Sin had been upon the throne. Hence we may confidently conclude that the second figure in the double-dates was intended to give the year of Rîm-Sin's reign which corresponded to the second year of the Nîsin era.