The correlation to the Western calendar was made two centuries later by Hendrik Doeff, himself opperhoofd of Dejima from 1803 to 1817, and an anonymous Japanese interpreter. They hypothesized that the person it had been issued to, jiyakusu-kuruun-heike, corresponded not to Specx but to Groenewegen (; Japanese medial [w] was written h at the time).
Two centuries after the calendar correlation was made, Hendrik Doeff and an anonymous interpreter proposed that jiyakusu-kuruun-heike, who received it, did not correspond to Specx but rather to Groenewegen (; during this time, Japanese medial [w] was written as h).